rex_rrracefab
You are probably referring to the tool that tightens the band around the cv boot, which is a crimping tool. SK tools makes one and is available at an auto suppy store, but hard to justify buying one for one use.

Ik Weet Niets!
Auto Zone (and probably some others) rents all the tools you need for free. (You put down a deposit and get it back when you return the tool.)