I haven't seen any. Usually just spare parts for more common systems, like the NES/Famicom, PS1, etc.
Well, I attempted to a region mod on a TG16 some time ago and succeeded. But in order to fit the switches inside the case where I had drilled the hole I had to cut into the PCB a bit right next to the traces for the card slot. Didn't nick any of them but the system sure doesn't work properly with it booting up with garbage on the screen. Figured out I severed a grounding line to the HuCard slot and fixed that with some improvement. While I haven't rewired the card slot bypassing the PCB entirely and heading straight for the requisite ICs I have a feeling the soldering to the HuCard pins may have knocked them out of alignment. Last thing I can think to check before I offer it as salvage.
