Mitsuboshi are 1 off the belt suppliers used by Kubota.
GENUINE MITSUBOSHI KUBOTA G18/G21 LEFT & RIGHT DECK BELTS AND PTO BELT SET
GENUINE MITSUBOSHI KUBOTA G18/G21 LEFT & RIGHT DECK BELT SET
Genuine MITSUBOSHI Kubota G18/G21 L/H Deck Belt P/N K5410-71410
SGL Belt for 42"" Cutting Deck Fits Kubota GR1600-II Part Number K5253-71420
Engine to Deck Belt Fits Kubota TG1860 with RCK48TG Deck Pn K5221-51350
Cutting Deck Belt Fits Kubota G1900-S with RC48-G20 Deck Pn 76505-34710