Fast reasonably-priced 35mm equivalent for the APS-C cams?

Maaaybe under $500, please? Don't waste my time with anything slower than f/2. All I've found is the CZ24, which I'm sure is a wonderful lens but is well out of my budget. Even the MF Rokinon's at $630. I see a Sigma 24mm at $550, which is almost there but leaves me wondering if maybe I should buy just the new Oly 17/1.8 for my OMD instead.