Look no further than Twin Cities Drum Shells.
I could not find a vintage Premier 18" floor tom to save my life!!!! And when I would find one, it would go for absolutely STUPID money!!!! I had a lead on an APK (not my preference, obviously), and it ended up going for $250, and it had extra holes!!!!
Pat will work with you. And Pat rolls his own shells. He doesn't do 20"-ers at the moment, and he doesn't do anything larger than 22", but he can do many stock sizes from a square depth to a custom cut. He will also do your edges for a very fair price.
I asked for a mahogany with birch re-rings 18x16" shell with a 5mm thick shell and a 1/2" re-ring. I also gave him the bearing edge angles of the shells I wanted to mimic. He got it done in just a bit over two weeks.
I don't have a bottom head on this drum (as the bloody bottom head is STILL not here, yet), and this drum thunders!!! Can't wait to get a bloody bottom head on it!!!!!
Pat used to be involved in a custom drum company, so this is not his first rodeo with building drums. Can't find what you want and know that Keller can't do it? Give Pat a call at (763) 221-7476.
I am not affiliated with Pat Budnick or TC Drum Shells and this is a testimonial from a paying customer.