OK, here we go again (after the data loss thing...)
A (partial) list of hair algae-eating critters that come to mind for a tank your size:
Large Snails - IME Turbo fluctuosus (Mexican Turbo Snail) is best. Half a dozen would be good in your case IMO, although you could get more intially and then give some away (or trade them back into the LFS) as the problem gets under control.
Conchs - One Strombus alatus (Fighting Conch) would be my choice in that tank. Queens are great too, but get too large too fast for most tanks (and definitely for a tank your size IMO).
Hermits - I'm not a big hermit fan, but IME Clibinarius digueti (Baha Red Leg Hermit) are a great choice if you like hermits.
Some other stuff I've never tried myself but has a reputation for readily eating hair algae - Emerald/Mythrix Crabs, Sally Lightfoot Crabs, Sea Hares, Urchins and Lawnmower Blennies (although IIRC you already tried one, right?)