This is wiki, add or correct sources as needed.
Some sources of these perpetually hard to find pots, often out of stock, keep looking:
- Amplified Parts (USA) / Alpha / https://www.amplifiedparts.com/products/potentiometer-alpha-linear-9mm-vertical
- Modular Addict (USA) / “comparable to Alpha” / https://modularaddict.com/parts/9mm-potentiometers
- Mouser (global) / Alpha / https://www.mouser.com/ProductDetail/Alpha-Taiwan/RD901F-40-15R1-B100K-00DL1?qs=1mbolxNpo8czbLgndpJJVQ%3D%3D
- Small Bear (USA) / Alpha / http://smallbear-electronics.mybigcommerce.com/alpha-single-gang-9mm-right-angle-pc-mount/
- SynthCube (USA) / Alpha / https://synthcube.com/cart/alpha-9mm-potentiometer-right-angle-pcb-mount-6-35mm-round-shaft
- Thonk (UK) / Alpha / https://www.thonk.co.uk/shop/alpha-9mm-pots/
- Tayda (Thailand/USA) / Alpha / https://www.taydaelectronics.com/catalogsearch/result/?q=A-1848
- AliExpress (search)
- eBay (search)
If you have to you can get by with the no-threads ones. Then you may have to mount the PCB to the panel a different way, e.g. by drilling holes for standoffs.
If you’re trying to search on Mouser, don’t click “PCB mount”. For some reason they have these listed as panel mount.