Just thought I'd add a few traditional watch strap shops that I've used in the past for my large collection of mechanical watches...
Check out
www.kainheritage.com for some really nice strap options. You'll need your own adapters but they make some really nice straps using some more exotic materials and the prices are reasonable for the quality you get. I believe they are out of Asia so the straps take a few weeks to come but they are worth the wait. I've ordered several for my traditional mechanical watches and have never been disappointed.
Another good site that I've ordered from for my mechanical watches that is out of Europe is
www.watch-band-center.com. A great selection of leather, metal, etc...if you're looking for a nice metal replacement they've got some very nice link and mesh bands that are of far better quality that most of the garbage people have been buying. Check out Staib and Vollmer mesh bands. Really nice and cheaper than the Apple mesh band.
Finally, if money is no object and you want a truly custom strap, check out either
www.thestrapsmith.com or
www.stonecreekstraps.com. Quality of materials and workmanship from both Rob (strap smith) and Jenna (stonecreek) are impeccable and well worth the price you pay. All are handmade and can be customized any way you like. Word of warning: they are very pricey.