The rapper broke his leg just over a week ago and needed surgery to fix it. The doc told him he might have to cancel his entire "Pretty Girls Like Trap Music" tour ... but Chainz wasn't having it.

So the rapper's producer hit up Sean Mahaney of Seanco Custom Wheelchairs ... and Sean tells TMZ his team got a tricked out 2-wheeler in less than a week ... in time for the tour's show in Tuscon.

No one's talkin' price, but we're told the chair set Chainz back around $10k. The cushion alone runs a G.

The pink wheelchair is propelled by 26-inch wheels with 144 gold spokes, chain-link detail that harnesses the wheels ... plus the rapper's "TRAP" logo. Sean's no stranger to tricking out wheelchairs. He hooked up Slim Jimmy for last year's BET Awards, which is how 2 Chainz's crew heard about Sean.

2 Chainz will perform the majority of his tour in the chair.

Almost wish ya had a bum leg, huh?