Searching for plastic guides for chrome mirror guards

Have an older medicine cabinet, the mirrors sliding along a track and have chrome guards top and bottom. Took the mirrors to glass and mirror repair store who sold me top plastic guides. I tried using them upon returning home but they were 1/4in. and they did not fit over the chrome guards which hold the mirror sheets in place. The mirrors merely sat in the track and moved back and forward as they were pulled and pushed back in place. These sliding mirror will no longer stay within the tracks without falling out.