One option would be ScaleLink drivers, they have 14mm spoked drivers (48" scales out to 13.99mm). https://www.scalelink.co.uk/ That said the shipping can be quite expensive and they are designed for British models so please carefully consider the nature of your project, your experience and risk tolerance.
What model are they from?
And do you need exactly 48 inch?
If you don't need exactly Greenway might be able to help. They show 45 and 51 inch,
https://www.greenwayproducts.com/products.php?prodCategory=wheelsets
I need 48 inch HO scale spoked drivers, but short of looking through every manufactureres page, I cant find a way to source them. Is there a list anywhere of steamers that used 48 inch drivers?