It's a little late to have them for this event, but I bought these last week and have since fallen in love with them:
valhallasurplus.ecrater.com/p/9799914/swiss-leather-gaiters
Rain and mud for three days, and my pants legs are still dry!
Also, wax/waterproof your boots. I'll be bringing my waxing gear, so if anyone needs teaching or a hand in doing it, come find me sometime in the afternoon on Saturday or in the lazy Sunday hours. If you plan on getting your boots waxed, you can pick up a travel kit at Target for $10, or you can use my brush and stuff if you pick up a tin for about $2. There's also some spray-on waterproofing solutions you can buy for about the same price. I prefer the wax, but it's a personal thing, not a matter of efficacy.