Anyone know where I can get a Wadia 861 board?

Did you try George Meyer AV?

If you were in Australia I'd have a look as I've been inside these a bit doing mods.
Cheers George

George Meyer was useless, no 861 parts
As for Australia; I can send you the board if you think you can repair the right channel output module? 
Please pm details if interested.

As I said in the email,  Unfortunately the only way to get just the board fixed, without the unit, is Wadia themselves. As they would have a factory jig which can power it up with all the different connections so then a tech can measure and fault find.

Cheers George