[ITSv40]

Agree with Greenvanman a local bearing supplier is your best bet. A quick Google has brought up: Hooper Limited and Barrell Bearings in Huntingdon and J M Bearings in St Neots, any of these should be able to help.

You will need to remove the old seal and take in as a pattern. They will take all measurements and most likely be able to supply off the shelf or next day.

I have an old Vintage ride on mower that I keep going in a similar way. The local bearing suppliers have enabled me to keep the old girl going and keep my paddock tidy long after the official parts have dried up.