The type of suit (called keiko-gi 稽古着, dō-gi 道着, or just gi 着 for short) usually worn in aikido practice is basically a judo suit. Some suppliers sell special aikido suits, which are much the same but have slightly shorter sleeves. You can wear a karate suit as well, although being lighter they occasionally tear.
It’s hard to find judo suits in Galway. Elverys Sports in the Corbett Court Centre and The Great Outdoors on Eglinton Street sometimes have a few but not always. In Dublin, Mullen Sports on the corner of Capel St and Mary St sells martial arts equipment.
There are loads of suppliers online: e.g. ninecircles.co.uk, which sells a variety of good quality suits and good aikido weapons as well. (From time to time we do a group order and split the postage cost. Let me know if interested.)
Aikido/judo suits generally cost c. €40–50. Check whether the suit you buy will shrink in the first wash. If not pre-shrunk, you may want to buy one a size larger. Here’s a size guide below (from the Nine Circles website).