30 inches seems like an odd countertop height, far to low...
Sure you measured corectly? What's the installation situation?
Cause I can't really remeber that ever being a normal height for DWs.
There are a few EU brand DWs that only are 32", but that's still to high for your usecase.
However, a single Fisher&Paykel DishDrawer would fit with a lot of room to spare - so you'd probably have to rig up some support structure from 2 by 4s or so...
Depending on situation, again can't say for sure, maybe one of these under the sink DW might fit? It's 34" high at the front, but the back bit isn't quite as tall.
Only the front 3 1/2 inches would be too tall for your request, the rest would fit.
Or, ask a kitchen contractor or so if the space could be re-done easily or if any of the above solutions can be made to work if you aren't handy enough for the job...