Depending on the weather, leg warmers do not replace tights. Tights+shorts keep your butt warmer, which is important. Below 8 deg C I wear tights, leg warmers from 8 to 15, and only shorts beyond that.

Maybe you could try to find a pair of tights that fit better? Wear your shorts to go try them on? But for this coming season just knee or leg warmers could do the job?

G'luck!