Hello AlexOC
A warm welcome to these forums.

Yes, the bearing carries were cast iron and were used from a Ransomes design.
These should be able to be procured from here or the UK.

The belt is a serrated type - to permit travel over small pulleys.
Again, it should be able to be replicated.

I have never seen that plastic replacement before on the LH side.

Hopefully, a member may assist.
Please let us know how you go..

Cheers
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Jack