Your predicament isn't all that unusual in these old design scopes.
The scope will have to be sent to someone experienced in such matters, such as Trace Scope Repair or maybe Korth in Alberta. Email or call them first to see if they will take on the job. From what I gather, with proper tools it's not difficult, just tedious.
Look up a member on this site by doing a search "Wheaty" I'm sure he could help you out, if he's still doing the work.