Getting spare parts for Quad ESL 63 ?

Brought my pair of Quads to an Audio Shop yesterday for repair assessment, the one speaker making a non-interrupted whining noise when plugged needs a one panel replacement while the other one has stopped producing the
" static campfire popping type noise " which was usually hapeening while being used here over the last 2 months.... a mystery for now ! .. anyone ??
Anyway I will need at least one new panel section to be introduced with the others. New panels availlable from Quad are very expensive so I am looking for other alternatives.... like getting a used one from previous owners or a rebuilt one from a repair shop..... any suggestions would be greatly appreciated.