Lightweight battery?

[alolympic]

I have a Clio 182 and am considering moving the battery to the boot.
Seeing as I am going to the effort (to give me more room for an induction kit) I am wanting to get a lighter battery.
I know there are lots out there but I need one that will keep charged even though the car will often be left for a fortnight without being run.
Anyone got any recommendations?
Thanks in advance

[alolympic]

Thanks for the response guys, sounds like the Odyssey batteries might be the right way to go.
I am happy to isolate the battery if it is standing for a while but wouldn't that mean I lose my alarm system? Sorry if this is a stupid question!!
Thanks