There are sellers on eBay and Amazon selling Rayovac 840 or 841 batteries.
Both of these contain 3 cells that can be replaced. The overall charge is only 800mAH.
Many of the vendors are selling originals that have had the cells replaced. The newer Rayovac 840 has clips that can be undone to disassemble the box. These don't have the red sticker on the top.
There is a cmpany called Dantona that sell their own versions with similar dimensions as the originals.
Model numbers for the Dantona batteries are "COMP-11SML" and "ULPC1844"
You can buy a 3x AAA cell battery holder and attach the original cable to it. The cells need to be arranged in series to give the 4.5V (3 x 1.5v = 4.5v). This makes a much larger box and my personal preference would be to avoid this type.
A battery specialist that can build batteries might be able to re-cell your old Rayovac. IIRC the cells are a custom rectangular, stackable, patented shape. These used to be used in 9v batteries (6x 1.5V =9v), but there is no guarantee that modern 9v alkaline batteries contain them.