Filco aftermarket is one of the oldest for factory boards, IIRC.
One of the most common Filco’s is the Majestouch 2, which primarily comes in full-size and TKL models. I have the full-size, and it’s what many vendors seemed to use until recently to showcase their keycap sets.
Here’s EnjoyPBT 9009 R4 on mine, it looks like what AliExpress vendors do:
Anyway, it seems that 90% of the available mods are for the TKL version, and they go back several years. Available on AliExpress, MechanicalKeyboards.com, and elsewhere. That’s primarily a previous generation of aftermarket parts that we’re talking about, though.
Since 2019 or so, there have been a number of efforts on GH to produce aftermarket modding parts for the TKL Majestouch [which probably doesn’t have that garish logo].
This guy designed a PCB for the Filco, and might be getting somewhere with it, and his useful post helpfully details some of the other ongoing efforts to produce aftermarket parts:
So it looks like new PCB and FR4 plates are items being worked on in 2020. That’s probably where to go if you don’t want to search around for years-old parts.