I looked at a few of my overseas contacts inventory .... only one is listing it.
CoinOp Express ... that's not good ... there wanting $795 for just the PCB (it's not worth that though especially when HOTD 3 for the Sega NAOMI is a far better earner). Some of their PCB's are reasonably priced and others their totally wacko on

I'd say it's worth $150 - $200 .... you might be able to get it off eBay for less (there's always some selling there backup after they get there main board fixed)
I'd say your best chance would be to hit the auctions and snag one that way.
Here's one of my contacts .... Julius always has a ton of Sega Model 2 & 3 PCB's on hand and he's real reasonable and does an excellent job on getting you the best shipping deal. JU707@aol.com (btw ... he has quite a few Virtua Fighter 2 PCB's for sell if anyone else is interested ... only $48 and there 100% tested and working ($14 shipping)

)
If he doesn't have it ... I would ask him if he would be willing to find you one ... I'm 99.9% sure he can track you down one.
He also has a House of the Dead gun on eBay for sell :
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=13718&item=3293250445&rd=1&ssPageName=WD1V (priced extremely low).