Glad to receive a little positive feedback on this (outside this thread).
Unfortunately (but not very surprisingly) after sleeping on it, the request parameters I had copied out of my browser yesterday evening have expired. Replacing with a fresh copy works, but this indicates that my session management could be greatly improved. Still easier than clicking through all the wishlist pages manually, but not as automatic as you'd really want. I'll have to spend some more time on this later. If anybody is a wizard with HTTP headers, sessions, requests, and so on, I would welcome any insight you can share.
Edit: worked on this some more today, but negative results only; haven't cracked it yet.