I think Class As with bunks (gas or diesel) only started being offered around 06-07 and initially it was almost exclusively gassers and they weren't all that common. Unfortunately, you'll probably have to look for something quite a bit newer (e.g. around 5 years old) or find a suitable floorplan that you can customize to add bunks yourself. If your budget does allow you to look at 3-5 yr old models, then pretty much every manufacturer sold a DP bunkhouse so there's some selection (although most of them are pretty much essentially the same floorplan).
As far as your length request, pretty much all bunkhouse DP floorplans are 38-40+ (one exception that comes to mind is Thor Palazzo but it's only been available for a couple of years). The bunkhouse gassers are mostly around 35-36' long. If you really want diesel bunkhouse of that length, you'll have to refinish the interior of something and you'll probably have to sacrifice a fair amount of living as most 34-36 floorplans usually don't have that much spare space (just finding a 34-36 diesel isn't trivial).
I do really like the Newmar All Star floorplan mentioned above but they are quite rare (supposedly Newmar built less than 50 in the 3 years it was available for sale) and they are a pretty high end coach so are not cheap (for a 5 year old, I'm guessing you're probably looking at $100k-$120k although since they are so rare, it's hard to really put a value on them (saw one sell at auction a few years ago for under $80k). Also they do have pretty limited storage so that's one issue with them compared to other DPs.