Call a local Locksmith, the chances are that he will have a key to get in, then sell you any spares that you may need.
A local caravan service centre may be able to help in a similar way, they usually stock a good supply of spare keys if you are able to tow your caravan to their premises for them to try them all to hopefully find the right one to fit.
Julia
------------- Just love to be out amoungst Nature and Wildlife
Celebrating 37 years of Caravanning in 2019, Recently Considered Retiring, but Totally Addicted for Life!
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most caravan keys have a number on them (wont help you this time) and if you go on ebay you can order spares. Keep one in your tow car/cars and you wont get caught next time.
------------- if your not living life on the edge your taking up tooo much room