Just seen this you probably already know about it but it's a good link
Replacement Windows for Caravans and Motorhomes

http://eeco-ltd.co.uk

They get a good write up but can, sometimes be pricey.

Used them years ago (when we still had a business) for a motorhome customer. They were very efficient and the window was perfect, even to the tint.

They are good at fitting tow bars. I had mine done there.