lost selector bearing spring on m4

[Shogun Mitsu]

Hey fellas, I was working on one of my guns & it seems I have an airsoft gremlin in my house (probably in the form of my 10 year old son). I lost 2 springs in one day, one I replaced by mutilating a pen but the one I can't figure out where to find a similar diameter spring for is the selector switch spring. It is the tiny spring that allows the bearing to be seated in the selected firing position. I was thinking maybe a spring from a lighter that holds the flint in place??? Any suggestions will be helpful. Thanks guys.

Nevermind, the spring from a Bic lighter is perfect to replace it, but you have to be sure to cut just enough so only about half of the bearing sits above the hole.