Hi Gottfried, welcome to the forum! Unfortunately because of a patent issue here in the US, we can’t buy or even see Simon’s whole UV range on aliexpress - only way I can see those products from him is to follow a google search link or try to fool ali into thinking I’m in a different country. Irritating.
If this is the light you have, it looks like it has a buck/boost driver in it (which is great…big improvement over 7135 regulation for UV emitters): https://www.aliexpress.com/item/4000307648927.html
That is a good choice for the light, overall, but also essential since it’s made for single or double cells, and when running two cells the voltage is too high for 7135 chips to handle, so a different approach is necessary.
Unfortunately that means that it’s not so simple to find a good replacement driver that has what you want and is also lower in output (suitable for UV…they are more sensitive to current and heat, not as robust as white emitters). They are physically pretty easy to change if you can do simple soldering and have a few basic tools. Basically you would need to unscrew the bezel, remove the lens and reflector, then desolder the two wires that attach to the copper mcpcb board that the emitters are mounted to. Then from the other side of the head you unscrew the threaded retaining ring (with circlip pliers) and can carefully pull out the driver from that side. I would assume that he is using a common 20mm size driver board in this light, but you’d have to confirm. The trouble is finding the new driver, though.
On the other hand, if you don’t mind using the light with two cells all the time it’s not hard to find a decent buck-only driver. Kaidomain (or their sister store on ali, the LHT Flashlight Store) have a few…not sure if they still have anything lower than 1500mA, which would appear to be the same current in the stock Convoy driver, but they might have 1200 or 1000. Richard at Mountain Electronics in the US still has a 17mm buck driver available in 1000 but the shipping cost might be prohibitive and you would also need to use a 20mm—17mm adapter ring to make it fit…or one for 22mm—>17mm if that is what is in there. 17mm 1A, 1,5A, 2A Buck Driver - 2.7V - 14V - 1 Mode He used to have a couple of 20mm versions but has not had those for sale for awhile.
For the most part 1500mA with that emitter is just fine, though…if running it for longer periods of time or in a use case that is different from a handheld light, the lifetime of the emitter may be shortened a little but it shouldn’t go Poof like when really overdriving with a lot of current. (I am assuming he is using the Luminus SST emitter…he used to have a nice model from LG but switched some time back to Luminus…but both are very good emitters that can handle the 1500mA nicely, much better in some aspects than the Nichia UV emitters.)
A buck driver is a preferred choice for UV emitters since they have a higher voltage need, which increases with added current, and that makes it hard for single batteries to keep up (they derate and reduce output somewhat quickly even with good cells, and heat exacerbates this). Using two cells and shedding the excess energy in a buck-regulated driver is more efficient magic and works well here. The boost function is great for single cells since it works to keep that voltage level up even as the battery depletes - so when the emitter is craving 3.8v but the battery has fallen to 3.6v, the light output doesn’t fall off a cliff since the driver raises it to suit. So…a buck/boost is great for UV but those drivers are scarce now. Buck only is an easier option, though. I didn’t know Simon was open to driver modifications but if he can/will do that, that would be great. If you change drivers, just be sure that the height of the components on the board will still fit into the recess where it sits (some inductors are quite bulky and some drivers use older tech vertical coil inductors that are taller, or the old ring-wrapped type).
You could also just buy a 20mm 7135 plain driver in the current and modes you want and put that in there for single cell use only. Works fine, but you just have to accept the lower efficiency and run time, keep a spare cell handy if you need to use the light for longer periods. In a C8 host those are slightly better than in the smaller tube lights like the S2+ since heat is better dissipated, but still some drawbacks.
Hope that helps you understand…wish there were a better quick answer and easier availability of the best drivers for this case! 