With no money outlay, for me, this is your best option.
Is the bleed effecting the front of house sound, or have you just noticed how bad it is when soloing the tracks?
When I've run the FoH sound for bands, I'm amazed at the bleed when listening pfl solo, (esp snare down vocal mic) but the mix sounds fine as it's blended and balanced as a whole by listening to the mix.
It's not perfect by any means, but you'll never completely eliminate it, one learns to deal with it I guess.
As for drummer vocal mics, completely agree they're a PitA (both the drummer and the mic). Especially if they won't help you out