A partial option is that any controller with analog triggers should work, especially as some driving games use them for acceleration (though I would assume remapping would work too). EDIT: One of the wikis says you may need more steps for analog triggers to work (on windows)

PCSX2 also now has a 'pressure modifier' key+setting (default is 50%) that may work in some cases (EDIT: specifically for digital buttons). At least if you have a key for it (like the OG Steam Controller has extra, like the grip buttons... change grip to keyboard key in sc-controller then bind that to the pressure modifier)