In the US, Home Depot sells them? They carry them or will get them shipped to store at no charge. From Looking online, Home Depot sells them as Polar Model 8386 (for the Tandem Axle "Walking Arm" trailer) or Model 8384 (for the Single Axle version). The specs appear identical to the models 8262 and 8233 sold elsewhere.
The Models 8262 (tandem axle) and 8233 (single axle) are sold by Northern Tool - and at least in the US, they sell for less than at Home Depot - they will ship to Canada, but the shipping charge kills any savings.