If you mean more than one chassis brand, I can’t think of any, but I suppose they could. There are plenty that import one, but also distribute others. Then there are those that import multiple lines, like maybe a kart line, and a seat line, and perhaps a bodywork line.
KartLift Kart Stands
DeepSeat Kart Seats
Don't bother PMing me, it doesn't work. Email is best: firstname.lastname@example.org.