I ordered 15 boxes (20 mounts each) of 645 glassless Wess mounts (product number DGX002) directly from the manufacturer just last month. The price was good and I received them in about a week (I'm in California). Not sure whether they are actually still in production, or just being sourced from dwindling inventory. It doesn't seem like they are being distributed anymore; if you want them, you have to contact the manufacturer directly, it seems. See www.wessmounts.net - all I did was give them a call and place my order. I have been doing this every few years for about 15 years and even after film's great fall-off have never yet had a problem.
Scott