Do a search for "Piney Mountain" .22 tracer. I found quite a few listings. A bit expensive at about $20/box of 50.

I've used their ammo. Traces very reliably out to about 100 yards.

Has worked well in all guns I've tried it in except, unfortunately, my M&P15/22. Would not feed in my M&P. Jammed about every other round. Tried both red & green. This gun had been reliable with all other regular .22 ammo I've used. Never otherwise have failures to feed, fire or eject. Something about this ammo doesn't agree with it.

Same ammo worked fine in Ruger 10/22, Colt Targetsman, S&W 41 and 17.

SBR also has a listing for .22 LR but I don't think they are in production yet. I've shot a lot of SBR's product in 9mm and look forward to trying their .22 version.