The $3-$5 clear yellow plastic head, wooden-handled "hammers" at ACE hardware work just fine.
When I say "snap" the sear pin head out from between the sideplate legs, I mean you smartly smack the head of the pin (flatly), causing it to snap down (to the right side of the frame) through the legs on each side of the pin.
I also mean you
never try to manually "spread" or "pry" them apart from around the sideplate legs. That's another way those legs get bent or tweaked, or broken off. A bent one that doesn't support its side of the sear pin can be just as bad as one that's broken off, if it isn't containing the sear pin and allows the rest of the sideplate to pivot and shift. That can change the tension between the slide stop lever plunger and the small angled front plate of the side plate, which means functioning problems can occur.
Using the end of a flat wooden wedge (or wooden cleaning brush handle), when you press the bottom of the sideplate legs downward onto the head of the sear pin, like in the pics I posted, the legs will snap apart just enough to allow the sear pin head to pass between them. Then, they'll snap around and be captured in the recessed groove of the head of the pin (because the head sticks up just enough for the legs to capture the pin's groove, as long as you have the right side of the pin flush with the right side of the frame).
Somebody online once posted some pics and video showing how they leave the sideplate captured between the legs, removing the sear pin with the sideplate. As an armorer, it can be sufficiently tricky enough to position the sear on the sear pin, by itself, with its tail against one side of the sear spring and the other end positioned under the hammer ... and then slowly insert the sideplate's pin through the 3 levers and the hammer, and not let one of the "Jesus" springs jump loose from under the levers.
There's a trick to holding the FP safety lever and the sear release lever
together, as a pair, and slipping them into the right side of the frame ... without having the FP safety lever's forward sharp point snag and pull on the little spring (sending it out of the frame, to end up in the land of lost socks). Some armorers like to use a punch as an 'assembly pin' (not fashionable to call it a 'slave pin' anymore, apparently), and install the 2 levers on the right 1 at a time, but it can be done holding them together, in just the right position relative to each other, and slipping them into the frame as a "pair", with a slight S-shaped wiggle (to clear the FP safety lever's point past the top coil, and under a machined spot in the frame).
MUCH easier to demonstrate, than to try and describe (as evidenced by the above confusing description), although the "wiggle" takes some practice. The first time the senior armorer demonstrated it to me, I could only shake my head and go back to trying to slip them into the recess 1 at a time.
Then, after enough bench hours dedicated to it, I reached the point where I was told by another couple of armorers that I made it look like a magic trick, and it impressed people in subsequent armorer classes.
The former senior armorer was a crusty, unrelenting task master.
Sorry for getting off topic.
Later ...