Sudesh,
Here's my fave; I have 3...one is 15 yrs old and still runs like a Rolex.
Battery Tender:
http://batterytender.com/default.php...7f49748c1c2642

As for hunting one down in N. Ireland or UK, or the continent,
try this link from their US site:

http://batterytender.com/deltran_europe.php

BMW, here in the Colonies, also sells the exact model, but it has
a Roundel on it, etc.

Any good brand, low amp, "floating/maintenance" charger should
do the deal. I keep all my cars and Scoots charged up on mine.
BR,mD