No matter where you go, you'll be on the bottom of the list of glass buyers because you've got a special order. The big buyers of glass will have an order in for a steady supply of glass so they will be getting thier glass every week but you'll be waiting for some surplus glass to appear or for the factory to make what you want. The thing you do get with buying the glass from the factory is the real specs. for the glass rather than the generalized specs for the glass type. In other words, just plan ahead. Glass takes a while to make and test so you're going to wait for anything that isn't already in stock. You might want to also check directly with O'Hara, and the other makers of glass for what is in production at the moment. United Lens (unfortunatly not on the web) is another place to go. Refractor glass is a rare beastie for those not hooked into the web of the few places that actually make it. Good Luck.