oilskins
Fark Hogman, you just reminded me that I have 400$ worth of oilskins (Burke & Wills) hanging in the wardrobe. Got them a couple of months ago from Kazzmazz in Kelmscot, and yes I did use them in the wet once, bloody good gear. Very warm and dry.
Bt
Yeah second the Rjays wet weather gear. Not their el cheapo range, but for $70 I got 'outer' pants that stayed dry after 3 hours in the wet at highway speeds...plenty of length, pockets, adjusters etc. and fit right over tall boots.