Free weight bar adapter. Two inch weight on one inch bar.

thingiverse

So you can use weights by CAP on a one-inch bar instead of a two-inch bar, and they may fit other brands too. Don't stand the bar on its end with weights on it because if the weights shear off the round outer part, they'll slide down and hit the other weights, probably knocking a hole in your floor. To store the bar without scratching the floor, you can put a small one-inch weight on the inside of the bar. Print two copies of the instructions - they're identical.