Hi George,
It's a long time since I lived in that area, I was born there. Worked for Neashams for about a year.
Is youy cylinder a pub bottle?If it is try your local watering hole. Most landlords will swap a cylinder for you in exchange for a few beer tokens.
Regards
Tony
.. or try your local fire extinguisher company - they must get their c02 extinguishers refilled somewhere