Or just buy some brass rod the same dia. and cut it to the same link + whatever. Slide it in-put carto on - push brass rod up and screw battery sleeve back together so it just puts pressure on the rod may have to ajdust the plastic disc near switch. you can just adjust it up and screw the screw all the way up as well if screw is long enough.
Just cut some slots for air with a Dremel. No need to buy anything.