Welcome. Try using the Search facility as this is a question that crops up regularly. Search this forum or the maintenance one or the equipment one. And tell us what caravan you have too!
You are unlikely to find original curtains (they would also likely be obscenely expensive as most original caravan parts are!) for your van, caravan breakers aside, which is probably a very long shot.
Google 'caravan curtain makers' and you will find a number of companies that will custom make them, or sometimes have a small selection ready made.
You may also find some off the shelf curtains from homeware stores that may fit, but generally they require modifying slightly (typically shortening), that's often within the capabilities of many a competent sewing machine owner if you know any.
You need to pay attention to how they are fitted to the van, and match the fitting method too!
There is a 'Company Directory' at the top of the page whereby if you click on the link you can find numerous companies that provide services related to caravanning and motorhoming etc. The one you require is the upholstery section which can be found directly in the link below.
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