Springfield Leather sells some very nice Latigo straps 72"+ long in widths 1/2 to 2". They use heavier weight for the wider straps. If this is just a one-off project this would be a cheap way to get some good leather.
http://springfieldleather.com/product/8226/Strap%2CLatigo%2CBlack%2C1-1-2%22/
I've ordered from Springfield half a dozen times or so and am quite satisfied. The couple times I called to ask about a particular side of leather, I got a salesperson who actually knew the product line... refreshing.
Mark
I have had a pretty good experience with Amazon. eBay seems to be mostly bargain hunters. Etsy and Artfire are ok but don't have anywhere near the market share of Amazon or eBay. It takes some time before sales really start to come in on Amazon as they keep you low in the search results until you have a track record. YMMV.
Mark