Suggest you go through your local NAD dealer and distributor.. IMO, trying to source a Frankensteined pre-owned board cannibalised for parts is a dodgy approach:
a) it’s a predictable outcome for failure to secure within any reasonable time frame , and
B) You’ve identified a history of board failures ,so substituting another pre--owned one ( even V2) that is also long in the tooth and lacking any warranty or assurance of future use is just ripe for a like step in disappointment with throwing good money after bad
FROM NAD:
“ ….We recommend you contact your purchasing dealer to discuss parts/replacement remote availability & pricing.
If your dealer does not have the part in stock you may contact our parts department to request your part. When placing your order, be sure to advise of your location and gear model number.
Canada Parts-Canada@Lenbrook.com
USA Parts-USA@Lenbrook.com
International Please reach out to your regional Distributor