As you care about Parallax Correction my guess is you are planning on shooting close up.
The location of the hot shoe (cold shoe, accessory shoe, ....) is different for Leica and Contax. While not that large in size, when you shoot close up it is enough to change the frame of view vs what is on your film. I don't know where the exact distance is where this becomes a problem, but a lot of it depends upon how tight you frame you image. My bet is you want it to be as accurate as you can, so I'd recommend you stay away from Leica or Canon finders. In addition to Contax (dahh) you can use Nikon finders as they have the same offset as Contax.
I can't speak to other vendors (e.g. Tewe Zoom, Kodak) which offset they were built for. I tend to frame loose and added an SLR for stuff that needed to be tight or was longer than 50mm. That worked for me pretty well, but everyone's journey is different.
I've found that finders keep their value pretty well so you might try several and keep the one that works best for you. Look at any money lost on resale as a rental fee.
Sorry I can't be more specific. Please let us know how you make out in your quest.
Thanks.
B2 (;->