Caravans Plus once had them along with most RV shops but once you see the price you will do what most of us have done and stuck it in with roof and gutter sealant.................... be very,very careful if you try to pull a bit of cable out with any of these side lights, you do not have much to play with, too big a pull and it will disconnect with the other end inside the wall somewhere......... very frustrating indeed.
I think when I broke one I did the Ebay thing, it was a close match and certainly way cheaper than shops wanted.
You will find the others will break as well if you try to unclip them ...........