
You'll have a bit of a wait, I'm afraid! For a start there's no such thing as a 'teacup' chihuahua (check the breed standards - if people try to tell you they're a special breed, they're lying). Also there's generally a huge waiting-list for chihuahuas, especially bitches (usualy at least a year) and they cost a heck of a lot more than EUR350 - you're looking at a price closer to EUR600 at a minimum.
Your best bet is to contact the IKC and get details of chi breeders in Ireland. Failing that, contact the breed clubs listed at the bottom of the
Long Coat Standard or
Smooth Coat standard and ask for contacts of reputable breeders.