You will need quite a hard rubber with the correct shore value, too soft and it will start to creap and the bond to the wheels will quickly fail.
Reason the commercial profioles are expensive is they are made to a specific pattern not copies of bumper strip an ddue to limited demand small batches will cost more than long runs. It is not square/rectangular but tapered and with a slight crown to the top.
I have seen Vee belts turned inside out and stretched over the wheels but they start to look fluffy quite qickly and never really look the part