I think there's a 2-piece you can get that just goes over whatever you're wearing. I can ask my co-worker (he rides in ANY weather... far more daring than I am). You will have to be more creative with footwear. Otherwise I'd just suggest some water-proofed military style boots (Bates). Several outdoor and LEO supply stores will Scotchgard items for you. Fees will vary.
Enduro suits are EXPENSIVE, so a shell, especially a 2-piece with an elasticized waistband on the pants would make the most sense, economically.
I'll get back to you... otherwise remind me with a PM.
**edit**
OK, so I asked my buddy and he tells me he uses Frog Toggs. Great product, not too expensive, etc. He picked his up at a bike shop in the valley, though he doesn't recall which. Looks like Google might have the answer, though!