Dave, I’ve bought from MylarPro, Sorbent Systems and others. I prefer Sorbent System’s products. But, with one exception, everything that I’ve bought that was touted as 5mil foil/Mylar laminate has been good, regardless of vendor.
3rdguy: Yes, there are clear Mylar bags. I use them to store bulk whole leaf. There are also some nice tin-sized ziplocs that are clear on one side. None of the clear bags have the exceptional barrier qualities of the foil laminates, though. Read through the Sorbent Systems website if you want to learn more about Mylar laminates.