I know other people have great success buying old leather jackets and skirts and using that material as well. Sometimes it takes a bit of looking around, but there's a sense of satisfaction in a great find. I also like that many thrift stores support good causes, so my purchase often goes back into my community.
Just make sure to inspect the hardware, and give it a good clean before using it on your bags. See below for how I used the belt.
Liliane Buckled Hobo in Retro Geek
I found the handle on my first bag was a nice size, but I prefer to have the option of adjustable straps, so I added some O-rings and a slider, and changed the strap to create an adjustable length.
The pleats on the exterior of this bag allow it to be a fancy purse with the right fabrics, but I think fun prints work too!