Surprise! I found a web site
www.pure-gas.org that lists places selling ethanol-free gasoline, byt state. I thought it was completely unavailable in my state, but there are a few smal engine and lawn equipment shops that sell it -- by the can, not from a pump. I called the shop nearest me and asked if they still have it. They do.
Price? A mere $27 per gallon.
So I'm back to removing the ethanol for mowers and small engines. But ethanol is an octane booster, so then I had to research how much the octane drops after the ethanol has been removed. So far, it appears the answer is 3 to 4 points, which means if I want to purify my own gas I should be buying at least mid-grade, or maybe premium. Hey, it's still cheaper than $27/gallon.