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First download the user manual (722 and 752 share the same manual) and look at the picture of the remote on page 15 and compare it very closely to a RH-75 that you will find on eBay.
Carver HR-722 owner manual.pdf
After looking at the manual these are suggestions, use your own judgement.
Carver Rh-75 Remote for sale | eBay
https://www.ebay.com/itm/257031732038?
As for remotes, two threads from 2010 cover a majority of the ones used in most of units requiring one.