Originally Posted by
smd4
Veloflex makes the Master 20. 20 mm and fairly cheap. I'll have to pick up a set myself.
Veloflex tires
Good sleuthing. I also searched, with no success. Cheaper than most car tires, per the OP's stipulation. And very good quality, no doubt. The quality is likely unimportant for a bike that's going to be hung on a wall, but good luck to the OP for finding anything cheaper in that size.