I use 1/32" thick spring steel (1095/85) that I get from Brownells for both the catch spring and the lid spring. They come in 1" strips about 12" long. You can cut the springs out with aviation snips. Then you just have to bend them and harden and temper them. I harden in heat treat oil that I also get from Brownells. Then I temper in my heat treat oven at 700F. You could also put them in a molten lead bath to temper them. If they are too stiff, you can temper to 750F.
If you use a hacksaw blade, make sure that you use a plain carbon steel blade and not a bi-metal blade. Personally, I only buy the bi-metal blades. The carbon steel blades don't last anytime at all.