Wanted: XT 10 speed Rear derailleur

I am looking to convert my 1x10 dually back to 3x10 temporarily for the 68k Convict course, so I can:
A) make it up the climbs and
B) not find myself spinning like crazy on the flats.

The short cage i'm currently running is not up to the job, so wondering if anyone has a spare long cage lying around and would consider parting with it?