My own creation from inspiration of several models out there.  I wanted something that would lock the trigger to an ‘on’ position yet allowed my finger to still use the trigger without significantly hindering its original operation.  Also needed something easy to print and that fit well to the new V15 model.  Bippidity-boppidity-boop, here's my solution.  

Print at 0.2mm height, with supports for touching build plate.  Use PETG for best results.  Be sure to align the two parts with the divets to allow the joint to snap together most easily.  

FYI - I used double stick tape to adhere to the vacuum, but hotglue will probably work too.

Update on 8-1-2023:  Based on feedback I tweaked the Lock part to be slightly more thinner on the top plane.  The net results is a more satisfying “click” into place at the top of the trigger.  I think this helps it feel more solid and reliable in depressing the trigger.  :)