Well... lets see, in total but not all of them at the same time;
Thumbs-Up CSEP mod 1, the #1 accessory and on all the time, cold shoe for my external finders and really adds to the hold.
Next is the Match Technical Service black 'bip', the best soft release I've used and just adds a nice feel to the release.
An Artisan&Artiest silk cord (white) ACAM-304 strap which is soft and comfortable, warps around the lens for storage/protection, and long enough for the across the chest style of use, and quick tying a small knot gives it the perfect length for the alternative over the neck and higher up in front.
Have a Ziess 21mm external finder which I love for its sharp big and amazingly very bright(!) view and matches the 24 Elmarit frame almost perfectly (Its black paint also matches the M9 BP).
A Leica 1.25x magnifier for those times I want my 50mm to be more life size in the finder or just a bigger view with a 90mm.
A Visoflex III to use with my 90mm Summicron with a short Viso focus mount for that ground glass (to see the depth of field) and 'reflex feeling' closer view (have an M-bellows too and can mount my 50 Summicron head for really close use).
A Leitz table top tripod with large head lets me put the camera on any flat surface (table, floor/ground, wall.. or non-flat against the chest, or as a 'gun-stock' into the shoulder) for slower shutter speeds.
And finally... a Leica black dot. Not that it does anything really useful, but with a black paint M9 sure looks nice 😎