The housing in good shape usually goes for $175-200. The finder should be included in that. The "chimney" finder is usually $70-90 and if you have to buy a 90 degree finder - they tend to go for similar price.
The chrome 65f3.5 arond $400-450 - the black 65f3.5 is consoderably more expensive $650-700.
The focussing helicoil for the 65 $50 and the other adapters vary, from $10-15 and up, depending on which one it is and how desperate you are to get one (dealers can smell this).
Ideally you should be able to get a "kit" with most of the stuff for $300 (not including lenses though).
It is not bargain basement, but there are enough Viso stuff out there to keep you happy for a long time - trying to figure it out.
The god thing is that Viso dedicated lenses are reasonably priced, 200f4, 280f2.8, 400/560 f5.6 and 8 are cheap for the quality.
It is a speciality item and you might have to scrounge around - best 'source is swap-meets and old, established camera stores that have been flogging Leica for a long time and places like "Real Cameras" in Manchester.UK who know what the stuff is and if they dont have it in stock, knows who has it and can get it.
Sometimes ignorance is bliss and stores take in a box of the stuff, not knowing what it is and are willing to part with it cheap too.
My rule is that if I see a Viso item and it is cheap, I buy it. It might not be useful, but can be used as a "trade" for something that I need ( or want). Even obscure bellows adapters can come in handy (though why I have 4 of the Hektor 125f2.5 adapters is beyond me - they must have been really cheap).
Enjoy the hunt
Tom