Johnathan Browning Mountain Rifle Percussion Lock Mainspring

[Uncle Al]

Greetings! I am hoping members of this forum will be able to assist me in finding a replacement for the broken mainspring in my Johnathan Browning Mountain Rifle. This is a percussion lock with an incorporated "set trigger" (after cocking, the single trigger may be pulled to fire, or it may be pushed forward to then become a 'set' trigger with a very light pull. I believe all JBMR's had this feature, but not certain.) Please contact me if you have one available, or could point me in the right direction to find one. Thanks in advance! Uncle Al (pics attached)