ACE Hardware stores have a good selection of springs. At least the ones in my area do. I found a nice one for my 1377 there. I ended up buying several because I didn't know which would work best when I got home (they're cheap). I ended up using the lightest one I purchased, and cut it down to length with a pair of wire cutters (it was a little too long as supplied).
I made a spring guide out of a door hinge pin, also purchased at ACE. If you get one of these, get the kind that doesn't have grooves on it. I cut it to length with a plumbing tubing cutter (a hacksaw would have worked too) and filed the head of it way down in diameter by chucking it up in a drill and running it against a file. The head is almost non-existent now, all that remains is a small shoulder to catch the spring. I got it to the best length by trial and error. I cut it too long intentionally, then iterated through installing it and filing it until I got the trigger to just barely release the sear and then stop. So the guide serves as a trigger stop too. There are lots of things at ACE you could use for a spring guide. Use your imagination. I bought some nylon spacers (about 1 inch long) but eventually decided on the hinge pin because of it's shoulder.
Two flat nylon washers (from ACE) sit on the sides of my trigger pivot pin now. I had to sand one down a bit in thickness since two of them are just a little too thick. Pick up some 400 and 600 grit sandpaper while at ACE - good for polishing the trigger and sear. A small amount of grease too. To finish up, I took the spring out of an old retractable ballpoint pin, cut it in half, and dropped it into the frame right above the front-top part of the trigger. This spring, plus the two nylon washers, got rid of all my side-to-side and front-to-back trigger wobble.
Be sure and check your gun for safety after working on the trigger. Cock it, without putting a pellet in, and shake it and bang it around (within reason!) to make sure it doesn't fire without you pulling the trigger.
