These are the tire options listed in the operators manual.
Continental 12.5-20 MPT E58 10PR
335/80R20 XM27 TL Michelin
335/80R20 Dunlop SPT9,
The Mitas tires on it are steel 3 ply tread, 1 steel ply side wall, rated at 4940lbs.
I've been searching the interweb and found these:
335/80R20 MPT81 NEW CONTINENTIAL TIRES (12.5R20). - Tires are subject to availability. - All prices are PER tire. Whether or not there is a forklift for unloading.
www.ebay.com
Tire used for example for the Unimog U423, U427 and U430. - All prices are PER tire. These are new never mounted 2012 DOTs. Whether or not there is a forklift for unloading. Typical use of military vehicles.
www.ebay.com