Not related to the seller, have no immediate personal use for the following, don't know if this is a good price or not, etc., but look at what eBay's search came up with for "Mondia"
200054029151
Vintage NOS Super Champion ~ Super Mondial Derailleur ; starting at $49.99.
This is a 4-speed derailleur. Probably suitable for bikes as old as I am (born in 1954).
yours, Joel Niemi / Snohomish, Washington, in the upper left corner of the continental U.S. map