Harry,
I live in Reading and had problems finding new frabric tops for my garden table parasol.
The manufacturer's sell this sort of stuff but Garden Centres don't stock it - you need to get the garden centre to make a special one-off order on the manufacturer.
I 'phoned Alexander Rose who told me that Dobbies in Spensers Wood could order it from them and sell it to me. I asked Dobbies to do this but nothing happened for several weeks until I chased it up. Eventually the parasol covers arrived and naturally I had to pay carriage on top of the regular cost.
I rather suspect that you will have to do something similar to get what you want - the key thing is finding the maker and asking them who sells their stuff in the area.
Good luck...
Peccavi
June 2009