I think *most* of the members here need the shallow depth cases more so than the deeper ones. We are on a VINTAGE drum forum after all. :D
Probably your best bet will be to simply ask if anyone has any SKB cases in these depths. A lot of the older guys on another forum I frequent all tried the SKB cases, but then decided to go with soft cases instead. I imagine the same experience may have happened here more than once, since many of the members are self-proclaimed "vintage drummers".
Or, cut down the cases yourself. The plastic is pretty uniform. You just need to peel off the fabric before you do so, and then stitch a seam back into it for the proper depth, and then glue it (I suggest Gorilla Glue and some clamps--I've done this more than a few times...).
Or, simply live with the cases you have, if space isn't that much of an issue. You can always throw a pillow/comforter/blanket in the cases to take up the extra room to keep the drums from bouncing around during transport. If you're just using the cases as drum set storage, you don't even have to do anything. Just make sure that if you stack these cases for any long period of time, that the drum case sizes are no larger than a 4" difference. I have a couple of SKB "stacks" where the 22" case has bowed in from the 16" case stacked on top of it, and the same with a 20" case with a 14" case directly above it. If you need to stack them, put a piece of plywood between the cases with sizable differences between them. I know this goes against the very idea of stackable, interlocking cases, but then again, they probably should have reinforced the lids on 20" and larger cases...
...dang! Okay, free association done...
singer