I have a classic Lady Comp with original packaging + accessories that has been gathering dust for the last six months, as I tried a Daysy monitor before just getting too lazy to temp at all.

Bought in 2011 for $485. Looking for $75 plus shipping. Pic is from an Amazon review, as I'm in the middle of a deep clean/purge at the moment.

You'd probably want to buy a new sensor from the manufacturer ($50 - https://www.lady-comp.com/order/accessories/).