We keep hearing mention of this 'different' connector for the monitor... could someone describe it please? It must be carrying the same signal, such that a pin swapping device could be pretty easily knocked-up to sort it back to VGA (XGA if you want to be fussy)?
Unless there's a compelling reason to have unique monitor connections, that nobody else in the world has apparently needed until now, the person who agreed to - or overlooked - that aspect of the contract should be hauled over the coals. Non-standard parts are the sort of thing an O Level business studies student could spot from 100 miles away as being a trap for a lucrative support contract monopoly, where 'specialist spares' just happen to cost 10x the market rate and need an approved technician to fit them...who happens to be from the original company. It's bordering on organised crime.
Personally, I would write into the contract of the contracts officer that they will be held financially responsible for any contract traps they lead the MoD into, where it would have been reasonable to expect them to have avoided them. That would concentrate the mind.