This page has links to the 25 known cajon makers in Spain. They are located in:

ABueno Percusion is located in Torrox (Málaga); Al Andalus Cajones is located in Madrid; Arlequin Street Art Percussion in Barcelona; Cajon DG De Gregorio is located in Barcelona; Cajón Flamenco Soler is in Granada; Camarada Percusion is located in Madrid; Carbono Instruments is located in ???; CHM Percusion is in La Alberca (Murcia); Dagmo Cajon is located in ???; D'Manue Percusion is located in Sevilla (Andalucía); Duende Percussion is located in Sevilla; Juan Heredia Percusión is located in Barcelona; Katho Percusion is located in Andalucia; Kimto Percusión in Marbella; LK Percussion is located in Córdoba; Malby Cajones Flamencos is located in Cartagena, Murcia; Manuel Moya Artesania Percusion is located in Granada; Mediterrania Musical is in Paterna (Valencia); Pjp Percussion is located in Seville; Ramon Porrina Percusion is located in Seville; Requena Percusion is located in Barcelona; Valter Percussion cajons are made in Spain but the company is based in Stockholm, Sweden.

YouTube playlist of cajons made in Spain:
Note that not all manufacturers have current YouTube videos. The list on this page includes websites and Facebook pages which may contain videos not on YouTube. The list on this page is current and actively maintained, the YouTube playlist is less frequently updated.

One photo per Spanish cajon manufacturer in Pinterest:

Listed above are links to the cajon drum builders in Spain as retrieved by Internet searches in March to June 2018. I am sure there are many others not listed. Please send me updates and correction if you have additional information. Thanks.