trigger parts for Hitachi NR 90AE round head stick nailer

[590138]

I just "inherited" a Hitachi NR 90AE round head framing nailer. The trigger lever is missing although it will still shoot since all of the internal parts of the trigger are still functional. There is a small round headed pin that I can see and this is what I have to press for the gun to shoot. I'm not sure of the additional parts needed to fix it besides the trigger (884-967) piece itself. I'm attaching pictures (thousand words) to give a better idea.
Thanks in advance for any input.