The bearings are from portable gas generator tire hubs. The 2 piece hubs are 8" diameter, air fill, rubber tires. Used for carts, dollies and generators.
Once the bolts are removed, the hubs will come apart.
• Air fill only
• 1/2" - 5/8" arbor
• Air fill only
• 1/2" - 5/8" arbor
In Canada: Princess Auto in Small Wheel Assemblies 2.80 x 2.50-4 Wheel Assembly@$15.99
In the US, Notherntool.com has "Northern Industrial Universal Generator/Water Pump Wheel Kit - Model# 2006Q000" for $33.00.
Also, look on Amazon or eBay for Generator Wheel Kits, dolly or wagon wheels
Check out this video for reference for a close up