Well, since amphibiaweb has this information:
"Alytes muletensis is among the most important species in Europe from a conservation viewpoint. The small occupied area, the low number of adults (between 500 and 1500 pairs in all, according to various estimates) and the evidence of a formerly much larger range - all bring this species to the highest rank in the list of animals deserving special protective measures. In fact, state and regional laws have forbidden the capture, keeping or killing of this species since 1980. Listed on the Red Data Book of Spanish Vertebrates as endangered, the species' rarity has also been acknowledged by all international conservation agreements signed by Spain.", it makes sense that few if any on the forums would keep these. You might try to contact Henk Wallays from Belgium. I think that he concentrates on Urodela and Gymnophiona, but he might know someone who is working in the captive breeding program or something. Good luck- it sounds as if captive breeding is the last gasp hope for these toads.