When your wife is wandering around an estate sale looking at furniture and quilting fabric, you sneak out to the garage and the basement and find all kinds of cool stuff. The Estate Sellers can't wait to get shed of old oil, ATF, solvents and other stuff the family will otherwise have to take to the County's hazardous waste facility. Boxes of real Ohio Blue Tip matches, old ATF with sperm whale oil in it, paraffin, bee's wax candles, solder. The older and grimier the garage or basement the better. Like the time I found an All American gasketless #23 1/2 pressure canner on a window ledge in a basement covered on cob webs and dirt. 50 cents said the seller with a question mark in her voice when I asked what she wanted.
Oh, and some of the hazardous waste centers will let you take things. Like a 5 gallon sealed bucket of mineral oil.