I have a working Tek 1502, and part of the removable battery box has started to disintegrate and needs renovation.
If you take the battery box out of the case, the broken parts are the top and bottom of the case, made from a hard shiny black plastic 13*5*1cm with cutouts for the cells. The two parts are bolted together, bolted to the external case door at one end and to the battery contacts at the other.
In the manuals the two parts are shown in drawing 4 as
drawing index:-9, part number:343-0349-01, qty:2, description: CLAMP,BTRY RTNG:W/HOLES
One option is to attempt to repair them using an epoxy glue strengthened with a glass or plastic fabric. Another would be to 3D print a pair, probably in nylon or "SLA". But if anybody has some for sale, that might be the best way. Neither QService nor Sphere have any, unsurprisingly.
I'm in the UK, if that makes any difference.