I agree with stk's suggestion to check with Rich but if he doesn't mention it you may want to ask him about getting a board from Flight Systems, Inc. in PA (www.flightsystems.com). They are an aftermarket manufacturer of Onan generator circuit boards at a much lower price than the OEM but I don't know anything about their quality, etc. Although their web site says that they have a 2 year warranty on the boards.
Flight Systems has Quiet Diesel control boards listed on their web site so maybe it's something new for them. Or are you saying they're just not available?
There are no Onan boards available right now at any Cummins warehouse when I look it up
Flight is now making boards for Onan Diesels as was mentioned and I'd have no problems saying buy one. I have used them and they are fine....and cheaper than Cummins-Onan