Trigger bar Spring -HELP ?

Hello - I am in need of a trigger bar spring and I have been told there are three differant lengths, this would be the longest one, my smith said it is not available, he has put in two shorter ones and they have jumped out after one and then two rounds fired - he said he could pin or peen one of the shorter ones in place but I dont want to violate the gun, is there any help for me out there ? This is my first time to this site - really happy to find it, Thanks a lot - Sandman