If you're mechanically inclined at all and like to tinker, I'd think you could find a seal rebuild kit for the brakes and stop the leak. Then just make sure you use the appropriate fluid when you put them back on the bike and they should last a while after that before needing any service again.

But otherwise I think a nice lower budget cable disk brake system would be a good route to go. You should be able to find Avid BB7s online for ~$50 per caliper/rotor. Then you'd need levers, which can be found for cheap. I bet you could have a nice cable pull set-up for ~$150ish.