I've no idea how many have been built, but I don't think I've ever actually seen one before, although I have heard of them. I'd suggest you'd be unlikely to find one but I may be wrong.
The vast majority of Pacs are 22' but I have seen a 40-42' cabin version. More recently they've been 24' but I doubt any 24's have come out of service yet. I saw a kevlar/carbon fibre version at Seawork last year, quick but at £400,000...
A few people have converted Arctic 28's to diesel inboard with reasonable success. Arctics tend to go for less money as not many people want the fuel bill that goes with a twin 225-300 O/B set up. Would give you something to do for a winter..or 3!
There's a guy called Phil who used to post on here who's bought & sold a few, I think I have his email somewhere if you want it.
Otherwise try here