On Amazon, just search 1/8 bsp to 1/4 npt adapters. They are listed as airbrush adapters, I actually just had to order one.

https://www.amazon.com/TIZZE-Connector-Conversion-Airbrushing-Compressor/dp/B078X7G66Q/ref=mp_s_a_1_4?crid=19AOUFZB26EOG&keywords=1%2F8+bsp+to+1%2F4+npt&qid=1642516856&sprefix=1%2F8+bsp+%2Caps%2C127&sr=8-4

That’s what I ordered.