Hi Laura,
First let me remind everyone that nearly all stuff sold as "Tibetan silver" is NOT silver and does NOT come from Tibet. It is basemetal silver colored goods usually from China.
There is not a lot of Tibetan products coming directly out of Tibet because of the political situation with Tibet as a "province" of China. Most of the Tibetan style goods today come from refugee communities in Nepal and northern India. Many "Fair Trade" stores and suppliers carry some selection of products from these communities. Ganesh Himal is one such "Fair Trade" supplier.
You listed many of the prominent jewelry and bead suppliers. There are others showing right now in Tucson and at various gem shows around the country. Pema Arts is the suppler behind TIbetanBeads.com you mention. They have several Tucson locations.