I got mine on the Convoy AliExpress store
Oh thanks found it, I was searching with the wrong keywords, centering ring and spacer and it was “gasket”
I also put together a C8 with 2mm WF a bit ago using convoy’s configurable linear driver. Did ~180kcd at the max ~7.5A.
As far as centering rings what I have done is just glue the XP or XM centering ring down on the MCPCB in the correct location. I find I can get it nearly perfect just by eye. I have even been known to use double sided tape in a pinch. 
Gluing it is better than using the 3030 gasket as it’s not always perfectly centered. Love the centering rings that are cut precisely for the led, not just a circle.
Nice to know. As it happened with my M1 with customized weird ramping firmware driver (current-limited to 5A theoretical by replacing the sense resistor stack), where the effective output current was a bit less at ≈4.75A. I also had to custom file a 3535 gasket back then, and ended up obtaining 101+Kcd on a cold start.
I am to build an M2 now, too. Reflector area wise, the M2 is 81.169% the surface of the M1. So, your build looks to be right as it is. 
Wed, 04/29/2020 - 06:48
What driver did you use?
How is that mcpcb being held down?
. Mtn.SRK 7135 driver 5.2amps at the LED.
. Thermal paste- Clamped-Thermal glue (very little)
. SBT90.2 and a mod’d Q8 driver is going to replace it soon…
Thank you
Installed the 2mm white flat into my L21A and get 1.35km at 1200 lumens ANSI. That’s impressive
Are you sure about the reflector size relationship between the m1 and m2? I was always under the impression they were much closer in ID/effective area…
I measure 25.6mm internal diameter for my M2. I believe the M1 is ~1mm larger. So that would mean about ~7% more area. Could you take an internal diameter measurement of the M1 please?
Nice results!
I have a L21A with 2mm as well.
How is your focusing and what driver did you use?
JaredM my calculations are based on reflector surface, which is proportional to r² or d² times height. This is where the 80+ish figure comes from (M2 reflector surface area divided between M1 reflector surface area). Reflector diameter and height figures taken from the Convoy store M1 & M2 reflectors' advertisement.
Barkuti, you mean r^2 or d
If I’m understanding you correctly, that is not the correct way to calculate the reflector area. It’s not the actual reflective surface area we care about, it’s the frontal area; the area apparent to a viewer far away looking straight into the beam. It is A=(pi/4)(D^2-d^2) where D is the large diameter and d is the diameter of the inner circle around the emitter that is not part of the parabaloid. Basically just subtracting the small circle area from the larger circle area.
I didn't mean to calculate the reflector area, I meant to have an idea of the relative area of both. That's it.
A = (π / 4)(D² - d²), EasyB? This cannot be right, in my honest opinion. If it were so, I could make a flat reflector (without height) and it would work fine throw wise. Reflector height and shape matters too, we know. Therefore, you may want to add height somewhere in that equation (???).
The shape of both reflectors is also a little bit different, although overall close. Even considering this EasyB's simplified equation could show some close comparative value here. Using EasyB's equation, the M2's area versus M1 is 81.706% (considering ∅31.8mm and ∅28.9mm M1 and M2 reflector diameters, and ∅7mm hole for both). This is to be expected, it is just missing a multiplication by the M2/M1 reflector height quotient to obtain the 81.169% number I got. 
But well, once I build my M2 we'll better know.
What matters is the frontal area of the parabaloid, assuming the LED is in focus, so when looking into the reflector you see it filled up with the image of yellow phosphor. The flat reflector you mention would not focus the light from the LED so you would not count it as effective area.
Consider just a flat domeless LED. It has a fixed area, say 2mm^2. Now imagine looking at it from the side so you only see a very small sliver of brightness. The light intensity at that viewing point is very low because the area of the LED apparent from that perspective is very low. The same concept applies with the reflector; just the apparent area matters.
Also the numbers you’re using for the diameters for the M2/M1 reflector are the outer diameters I think, not the diameter of the reflecting area. See here for measurements.
Technically yes you can make a reflector without height, called a flat mirror, however the focal point would be at infinity so your LED would have to be inifitely far away.
You can make a shallow recoil reflector, with very little depth, and as long as the LED is at the focal point yes it would throw the same distance as a deep reflector with the saame front area.
Play around with the Reflectors #1 and #2 changing their diameter and focal distance, you will see how the parabola changes shape.
While the depth of the reflector changes how many lumens are collected, the frontal area is what determines throw.
Thanks for the contributions. I just took naked eye caliper measurements of the outer diameter of M1 and M2 reflectors looking right in front of my M1 and my M2 host: ≈27.6mm for the M1, and ≈25.4mm for the M2. Substracting the area of a ∅7mm hole in both cases, the M2 reflector front surface area is ≈83.641% that of the M1.