You can find the accommodation offer of San Javier and other nearby towns such as Santiago de la Ribera, La Manga del Mar Menor and Roda on the website of the Tourism Department of San Javier.
https://turismo.sanjavier.es/en/
On that same website you can directly make your reservations.
https://turismo.sanjavier.es/en/reservation/
Phone: +34 968 571 704
E-mail: santiagodelaribera@sanjavier.es