Just thought of another option.
You mentioned having a Fandyfire 501B and I found
SKU 3731503. It's a complete drop-in module listed at 1000lm and has only 1 mode. Super easy to install too. Just unscrew the bezel on your light and the entire module will drop right out from the front, then drop the new one in and screw the bezel back on. If more brightness is all you need from your 501B, it should help, and isn't much money. Don't know why I didn't think of it sooner. Old age I guess. ;)
I checked the pics and it looks like a genuine Cree LED, but I can't be positive they haven't got clones now. You can ask Anniepan to confirm it if you're interested.
I just need one more flashlight. Just one. Honestly. :D