That's so annoying pal, i feel your pain!
After so many years of riding Id say it's Worth spending and getting some up to date hydraulic discs.
Old mag's were always a pain in the backside for me. There are plenty of better options these days that from experience seem to last longer but that could just be me.
Back in the day We had to use sticky tar from the roads on our rims to get anything decent out of Magura most of the time. It was a great hack though to be honest!
Like monkey said If you're desperate people do tend to have loads of spares knocking around not doing anything. Mine got stolen recently unfortunately or I would have offered them to you for free.
Good luck though!