My front hood drainage hose was disintegrating. I ordered several standard sized hoses from U.S. companies but none of them fit correctly.
Finally I located a supplier in England who had metric sizes. I found one which was a very close fit. Sent Lee Hedges a sample to get his opinion. He confirmed it worked for him.
The hose is located at www.VintageCarParts.co.uk . Order the tubing that has the 10mm bore and 1.55 wall.
