Doug at Ships' Mechanical told me they can be re-framed. You might talk to him & see what your options are?
I will be on the lookout for a new rear door also. Hoping someone makes a fiberglass unit with an aluminium frame but not holding my breath...
Current fleet: '85 Ninety 3.9 V8i Auto SW, '95 Discovery (restoring it for my Nephew),'07 BMW 335Xi.
Past Land Rovers: '96 Discovery SD, '00 Range Rover HSE, '04 Discovery SE7, '07 Range Rover HSE, '08 LR3 SE7.
Past fleet: '89 Classic Mini, '83 Porsche 911 SC Coupe, '89 911 Carrera targa, '96 911 Carrera 4, '07 Toyota FJ Cruiser, '04 Mini Cooper S, '11 Mini Cooper S Countryman All4.