I couldn't find a link, but this was on Amazon:
NaturesGoodGuys
3.8 out of 5 stars 191Reviews
NaturesGoodGuys Live Beneficial Nematodes Hb+Sc+Sf - Kills Over 200 Different Species of Soil Dwelling and Wood Boring Insects. (5 Million_Nematodes)
$19.99 + $1.25 shipping
Hb and Sf kill fungus gnats, and Sc kills fly larvae and a variety of moth larvae, so it theoretically could get fungus gnats and drain gnats, both.
