Cheapest upgradeable discrete graphics/MXM system?

Anyone able to recommend a cheap laptop/notepad with upgradeable graphics? I don't need to desktop replacement system, and not worried about battery life as will be mains powered.

It's to cover emulated Amiga games, DOSBox, and old PC games that ran fine on Nvidia 6800 era cards, e.g. Homeworld 2. But have the option to upgrade should I play more recent titles without needing to replace the whole unit.

The problem is systems with upgradable parts are not cheap at all, if you want a system that will play older games, and newer games, you want a 4xxx chip, again they are not cheap, you do not hardly get any upgradable lappies.