Oven thermostat knob lost or broken

An all-purpose hardware-store knob didn't work, the shaft was way too short.With the aid of the Part-Select diagram,I found the correct stove model number. The simple little Tappan oven control knob cost over $30. I checked other appliance part vendors on-line, but found their part descriptions imprecise and equally expensive. I ordered the part and it arrived in 2 days and worked perfectly. An appliance store had told me I wouldn't find a retrofit on such an old stove and I would have to buy a new stove!