There are many kinds of waddle/spreader pants out there, and yes- many of the best come from Über-kinky Germany.
What are they? basically some sort of clothing that increases the bulk between your legs, or spreads your legs apart, forcing you to waddle (if you can), or be forced to crawl. It seems like there are 3 major syles.
1. Padded crotch- a pull-on diaper cover, sometimes in form of a onesie or overalls, with very thick padding in the crotch. Great for people who love a huge, obvious diaper. Not substantial enough to actually "force" you to waddle. (A similar effect can be achieved by just wearing more layers
2. Spreader sheet- a pull-on diaper cover, sometimes in form of a onesie or overalls, with very a sheet of rigid material in the crotch- like a rectangular diaper-stuffer, except made from firm plastic. If the plastic is thick/strong enough, it is literally impossible to bring your legs together- forcing you to waddle. The downside is that it's very uncomfortable, and kind of unnatural looking . . .
3. "Spreader pants/harness"- a body harness that (relatively comfortably) forces your legs apart, making waddling difficult, and typically reducing the person wearing them to give up and crawl. I've seen a couple of crappy imitations, but here is a link to the real thing:
http://www.adultbaby-shop.com/shop/en/Special-spreader-pants (fyi: I dunno if this link is a re-seller, or the original producer with a modernized storefront). I reaally want one of these!!