I wrote Es Garrover de Mallorca a couple times to find out if they're distributed somewhere near me I can walk in and buy. They haven't replied. https://esgarroverdemallorca.com/
So I figured I'd look into health food stores in Bilbao as the most likely places to carry carob products. I wasn't sure which one to try. Luckily, I didn't have to choose since I ran into one on the way home.
They'd never heard of carob syrup, but they had two different brands of carob powder.

