Byrna, from your avatar it looks like you're in Portland or somewhere nearby (Beaverton?). I'd recommend talking to different bike shops- there are different types of chain/pants guards that can be adapted to various bikes. I would talk to Clever Cycles (on Hawthorne) or Citybikes (at Ankeny & 8th). They may be a little more helpful.

Greasy, dirty chains are a fact of life here in Portland. "Wet" chain lubes last a long time but tend to attract dirt while "Dry" lubes don't last long in our climate. The "perfect Portland bicycle" would have an enclosed drivetrain or weatherproof belt drive.