I make them and "nailbender" on CPF does also or you can make one yourself, here are a couple how to links to look at.
There are quite a few advantages to custom drop ins. You get many different options such as:
1. Any emitter and tint you want.
2. Maximum drive current usually from 1 amp up to 3.8 amps for an XML, but the sky is the limit here.
3. Mode selection my favorite is a custom 5 mode from moon low .002 amps to turbo 3.5 amps 1 to 900 lumen with the press of a button.
4. No visible PWN if that is bothersome to you it can be all but eliminated with a custom driver.
5. Reflector option SMO smooth or OP orange peel and different sizes as well.
6. Potting, you can have the empty air space filled with heat conductive adhesive to increase the heat sink abilities and increase strength for say a weapon mount light.
7. Spring size and position, don't laugh P-60 hosts vary so much different spring sizes can be required and heavier gauge spring flow more amps with less heat.
Basically anything you can think of can be done on a custom build, plus doing it yourself is quite fun and satifying.
If you can solder you should really try building one yourself.
For Sale thread