One avenue is to find a pair of cheap pants, let them take their lumps, and then replace them. My own belief is that such a tactic might be more economical for you in the long run. The foremost solution for this approach would be to buy a pair of Marmot Precip Pants ($69). OK, they don't have a side zip, but they're super light, comfortable, and waterproof. Marmot's Guide Pants ($190) are also a very nice option, with full zips and equipped with Marmot's proprietary MemBrain technology, which allows more water vapor to escape as you warm up. Roughly between the two you'll find REI's Alpine Lakes Pants ($98). These use an REI waterproof-breathable laminate, have a full side zip, and employ ripstop construction for decent durability.
After that, things start to get expensive. One really nice pair of pants is the Arc'Teryx Beta AR: three-ply Gore-Tex XCR, reinforced knees, and well-fitted for ease of motion. Alas, they're $300. Ditto for Mountain Hardwear's FTX Ultra Pants, very similar to the Beta in design and construction, but five bucks cheaper.
All things considered, I'd go with the Marmot Guides or REI Alpine Lakes. I think they offer the performance and features you need at a reasonable price. Then, buy some patch material!