Source for large double-spur auger bits

My students often ask where they can find a good double-spur auger bit like the ones they use in my classes. I've collected mine over the years, and don't have a good source for them. Looking for 1-1/2" and 2". CB.

I've found 1.5" Greenlee and Milwaukee bits on ebay on occasion. I generally look for what I think are Jennings pattern augers, they have less meat on the outside.

The only 2" double spur auger bits I've found new are made by Northwest Bits. They are available from some of the log home supply stores but they are pricey.