Does anyone know where in the Greenville, TX area I can purchase 20% vinegar?

If I were you, I'd buy 10% vinegar. It is safer to use. You should be able to get 10% or 20% at most gardening or feed stores in your area. Since I don't know your area, I'd suggest you look in the yellow pages and call sources to find what you need.

pattyranch-
All the Lowe's stores in Texas carry it in the organic section. I'm guessing Rockwall, Longview or Tyler are the closest to you. If you need a 55 gal barrel, let me know.
Tony M

Thanks to all for the replies. I'd checked with Home Depot and they don't carry the 10% or 20% vinegar. The gardening store in Cash, TX quit carrying the vinegar some time back. Will definitely check Lowe's out.