I actually use no-name Vachetta straps that I purchase directly from a leather manufacturing company (I believe they're out of Texas).
I started doing this because I always wear copious amounts of sunscreen (I live in Phoenix, AZ) and I was ruining my Louis Vuitton leather. These replacement straps are still 100% Vachetta leather (and, will actually patina the same way as LV leather), but are incredibly inexpensive, so I don't care if I ruin them with lotion/sunscreen.
I'll have to go through my email to get the company name/website, so in the meantime, here's a link from an ebay store that carries them:
http://www.ebay.com/itm/3-8-in-Vach...t=LH_DefaultDomain_0&var=&hash=item2ecfdc3e08