I did it a little bit different. i used a Tactswitch with a long stem behind the trigger and placed a spring over the stem to make it go back.
i found that the tact switch was the same width as the trigger, i don’t have any part numbers i used stuff i have laying on my bench.
closest would be this switch http://www.taydaelectronics.com/tact-switch-6x6mm-11mm-through-hole-spst-no.html.
i might be able to make some pictures of how i did it