I can't help you about a camp site near Le Boulou, but i wanted to let you know that children are on holidays since yesterday. That means that people who want to ski in the pyrénées are going to take the motorway since all the roads are closed because of the snow from Ax les Thermes down to the pyrénées. Today is mentionned by the "traffic authorities" as an orange day and even as a black day on the roads leading to the mountains (Pyrénées and Alpes, much more Alpes though).
So you might find 1) a lot of traffic and 2) the very few opened camp sites all booked.
Think twice before leaving Parc verger, tomorrow might be better;
I can't still offer you to park at home which will allow you a stop before being stuck any where .
It's up to you, but if you want to stop home , let me know!
Have a safe travel!