hp41cv memory lost

[Walterthomas]

I had a battery leak and corroded one of the contacts. I cleaned the contact and the HP works fine. My problem is every time the contact corrodes or I replace the batteries I get "Memory Lost" and the programs I have in the HP are gone.
Is there an internal battery or something that maintains enough juice to retain the memory when the batteries are replaced?
If yes, can it be repaired?
I did a search for internal battery HP41 and got no results.
Thanks in advance.