I always make my own. Never have bought a single trigger. Triggers are fun and easy to make and trigger plates are not bad to make. Most of the books on building ML guns have sections on this.
Trigger: I start with a piece of cold rolled steel about .100 in thickness and an inch and a half square, lock it in the vise with 3/8" sticking up and start beating on it with a ballpeen hammer where I want my finger to touch the "shoe". Cold rolled steel easily dents and expands and directing your blows at angles makes a nice wide rounded shape in cross section. Scoop it or not as much as you want, so the trigger shoe can be straight or curved. Make this area extra-long if you want a curl on the trigger. When you have the shoe area done and still have plenty of extra "on top" for the part that goes into the stock, take it out, reposition, and use the hacksaw to advantage. If you want the curly bit, cut quite a bit right against the peened wide area so you have this nice and thin for curling. The curling is done hot, AFTER you've cleaned everything up nicely along the "shoe" with files, focusing on the backside of the shoe.
I then beat the trigger body with my favorite hammer on the smoothest part of the anvil to thin it somewhat and smooth any digs the vise gave it. Use calipers to see if it's even thickness. Then hacksaw to correct profile to fit in the gun.You may have to file some areas. I use a "flatter", a blacksmith tool that I place on the side of the trigger then smack with a 4 pound hammer. All this stuff works best of you keep your hammer faces smooth and yoour anvil too. The surface of the steel compacts and looks great by hammering.
That was the really fun part. Now making the plate: I forge this from stock about 3/8" square. I leave a front "lug" about 1/4" high for the tang bolt to screw into with plenty of threads. Then I cross-peen the length to taper its thickness and also I taper the whole business until I have a piece about 3/8" wide at the front, 1/4" as I said where the tang bolt goes, and about 1/16" thick toward the rear. It forms a boat shape looking at the plate from top or bottom, with a sharp "prow" to the rear and a blunt "transom" at the front where it is thick.
OK that was still the fun part, now we have to slot the little devil. laying out the slot is best done carefully and thoughtfully as this is where you show your workmanship. Make a little model with thick paper of the trigger and plate and make sure the tiigger will fit in the slot and not have a lot of slot left over front or back. Tricky.
Everbody has their way of approaching this but lacking a drill press, and hating wandering drill bits, I have a crude but effective method. I draw the line for the slot and then smack it devilishly hard with a sharp cold chisel on the line on both sides, top and bottom. Then I smack it devilishly hard with a dull rounded cold chisel right in the V-slot I just made. This forms a great guide for drilling. The bit cannot wander! I flatten the plate of course with a couple of hammer blows before drilling. I drill as many holes about 3/32" as I can stand then start working with chisels and hacksaws and files, as the mood strikes me until I have the slot clean and straight and the trigger fits in it. I tried making a broach but it broke first try.
