The simple trigger, as it is called, will do just fine. I usually try to put a little u-shaped piece of brass at the top of the inlet to form sort of a bearing surface at the pin hole. I don't know if it helps anything or not, but it makes me feel better, especially when the trigger slot is close to the lock inlet. There is not much wood left for the trigger pin on the lock end.
As Eric indicates, a trigger plate is not hard to make. I use 1/8" flat bar from Lowe's and cut out the shape, which can be anything from a fancy shape to a simple rectangle. Drill a series of holes to start the trigger slot and clean up with needle files.