I ordered both the 13" & 14" but thought the 13" looked better on the car. https://www.carbuilder.com/uk/14-wood-rim-steering-wheel-70mm-pcd (you can change size to 13 on site)
The boss was sourced on Ebay https://www.ebay.co.uk/itm/193720741129 but had to be drilled as the 3 holes did not line up with the Morgan boss, but not a major issue.
Hope that helps guys.