Dikembe Mutombo -- Being Tall Ain't Cheap ... Gotta Custom Make My Suits!!

It's hard to shop for clothes when you're 7'2" tall ... just ask Dikembe Mutombo -- who tells TMZ Sports it's too hard to find threads that fit on the rack, so he gets everything custom made!

Problem is ... bespoke suits don't run cheap -- and according to Mutombo, a good quality outfit usually runs between $1,500 and $2,000-a-pop!!!

It's a good thing Dikembe (reportedly) made about $143 MILLION during his career.

We also asked D.M. about his sleeping situation when he's on the road -- how does he find a bed that can fit a 7-footer?!?

Seems he has better luck at hotels than he does at rental car spots ...