I was Framed!

Does anyone know where to find the 'Hecho En Mexico' frames that turn up on all kinds of art in most thrift stores? Specifically, we're looking for a wholesale supplier of the black (or unpainted) frames with the linen insert shown here...

We have quite a few in random sizes and colors but would love to get a bunch of new ones direct from a supplier. Potentially risky trips south of the border would not be our first choice :)