Hi Steve,
If it's like this:
Charlie's option would be cheapest and easiest: "Is there an option to skim the shaft to fit different seals with slightly smaller ID seals?"
Failing that you could get the diameter reduced and "sweat" a sleeve on it and have that turned & ground to size.
You could try Robton engineering for a price. https://www.robton.co.uk/
But there's probably plenty of firms over your way.
Jim