Postage EU/UK to the US/Canada, and vice versa, is also extremely expensive these days/
There are other large format SLR options, I have many in my restoration pile. Largest is a Thornton Pickard whole plate Ruby Reflex, that 8.5" x 6.5", and I have quite a few 5x4.
I can't speak German, just find a Mentor on eBay.com from Germany, then change the .com tilde to .de and refresh, and you will see everything in German. You can cut & paste to do a German language search.
IT's definitely worthwhile, I have bought a lot that way over the last 20+ years.
Ian