The bearings are a std size and can be got from any bearing supplier, such as a SKF agent, just take along old ones, or measure first, inside outside width, they don't need to be heavy duty or anything as the load is not really noticed in bearing terms.
You'll end up with a number like 50-70-15(this is made up example), this is how std ball race bearings are sized as well as std type oil seals.
tabetha