Here are the parts. I am assuming who ever does this knows how to get the trigger out..
All I did, was make wedge shaped metal plate, that fits in between the two parts of the trigger. It should be snug, but still have a little play in it, or the trigger block won't work. When put together, the trigger should look like this.
And the added part. The important thing is the wedge shape, and the hole in the plate needs to be tight when it's assembled. Just trial and error. File some, test, file some, test. And so on until it fits.