Pair of serious boots
While I was in Kaplan's — the place where I got my Army raincoat — I also got myself a pair of serious boots. These fellas are Carhartt, a brand that specialises in workwear and military-use gear. I think they were pretty much the best pair of boots in the shop: thick-soled, hard-skinned, and waterproof; and yet reasonably flexible and comfortable as well. Orthotics fit in them just fine.
From now until the end of my trip, these are what I'm going to pretty much live in. My flimsy runners are already in the mail, on their way back home. It's time to get serious about this backpacking stuff.