Front Panel Express
Good suggestion Bunker if someone is going more the DIY route. While yaeltex has definitely got the most options with a turnkey system (like they do joysticks), and their software configuration software gives you lots of flexibility (like it has NRPN built in), nothing can beat the DIY approach for doing the most flexible design, if you can and are willing to do the work.
Yaeltex is no doubt laser cutting their front panels, for their one off designs. And they do provide the printed graphics too. The back of the enclosure they do in wood, which is a very friendly option for DIYers. FPE can do metal backs for the enclosure.
There’s a yaeltex thread at Elektronauts. BTW: I don’t think yaeltex is expensive at all, considering the work involved in quality custom one-off production. You don’t compare price of a one-off product to those being mass produced.
Adafruit is one good place to pick up electronic hardware as a part of a DIY MIDI controller project. Here for instance is a link to their backlit LED arcade buttons:
You can get depth dimensions there. They also have ready made backlit matrix buttons — see Adafruit Neotrellis, and a complete line of other stuff at Adafruit, to do a DIY MIDI controller.