You can get soya milk in at least two of the supermarkets, definitely in Alex's and the other one on the beach road (can't remember the name).
There are two types - a 1 litre carton, the name escapes me but the carton is green, it was a bit pricy at around 4 euros, and unfortunately it was the kind that curdles easily.
In Alex's they had small 500ml cartons, I think they were white & blue(ish!), they were under 2 euros so cheaper than the other one, and in my opinion much better tasting and no curdling.
They're both easily identifiable as soya milk.