check out REI's house line of pants/capris. There's some of them with a lot of pockets. Any one that's a softshell or nylon with dwr will shed water. Not specifically made for biking. You could maybe look at patagonia. REI'll be cheaper than patagonia, but a lot of outdoor stores are clearing things out.

If you wanted to make your own waterproof pants - you can buy the waterproofing stuff that they use to renew DWR finishes on outdoor gear - check out nikwax. Spray that on something like nylon, and you'd be in reasonably good shape. The nylon'll quick dry.

http://www.rei.com/product/724688