Marathon Universal Fit Pneumatic (Air-Filled) 14.5-inch Tire and Wheel Assembly, Replacement for 4.80/4-8; 4-8; 4.80-8; 4-6; 3.50-8, Wheelbarrow/Cart Use, Castle Tread in the Wheels & Tires department at Lowes.com
Amazon.com : True Temper T22CC 8 in. Hub Tubed Wheelbarrow Tire Wheel with Ribbed Tread, 8-Inch, Black : Wheelbarrows : Patio, Lawn & Garden
13 in Pneumatic Wheelbarrow Tire & Assembly by Farm & Ranch at Fleet Farm