It is a B&O designed and built set and spares were available from spares stock. The important word here is "were".
They will be obsolete as far as B&O are concerned and your decision is do I really want to spend money on this broken one when I could buy a good used one (complete set that is) for maybe £100-150. Since the cost of a new board will be much higher than this it is a no brainer!
Alternatively, you could contact "nobby" (Neil Briffett) on this forum who more than likely will have s/h working boards, complete sets in good condition or cheap advice!!
As another alternative, I have a good working MX4000 as my office TV which Is soon to be replaced by a BV1 and could be yours for £150 cash (no remote).
I'm running out of alternatives but buying a new board would be the last thing that I would consider.