Vortex seems to have control over that set, and iKBC (who I believe is affiliated with Vortex) used that exact PBT set on their black and white RGB keyboards.
There's also this:
https://mechanicalkeyboards.com/shop/index.php?l=product_detail&p=1330Font's the same as the original white YOTG ABS keycap set.
The keycap bleed is a bit weird and inconsistent; PBT bleed doesn't seem to be as uniform as ABS (like the really nice diffused and even bleed on the Ducky YOTG keycap set) and some keycaps may have a darker square type layer (where the stem is)blocking part of the bleed through the keycaps (not the legends of course), but my set only had that on a few keys on the number keypad, INS, and a couple of the position keys (I think scroll lock, pageup, Calculator, etc). Wasn't on any of the main number or letter keys, just some keys on the extended keyboard part. Keys look great otherwise and perfect with the LED's off or in a lit room with the LED's on. If you're not OCD, go with either the white or black set. The white set lets more light through the legends for some reason, while the black set lets less light through (and thus looks dimmer) but there's of course zero backlight bleed whatsoever.