Hi Matthew,
I'm pretty sure you can get smaller versions of the one I have as it is pretty heavy (maybe 7kgs...?). Also mine is a sealed battery so no worries about ventilation. When mine is not in use it lives on its charger as the guy at the shop recommended, and it can be discharged pretty much all the way without any problems.
I haven't had a full night out with it yet so I don't know how long it will last in practice but in theory it should last well over 10 hours with my setup.
Here is a pic of it for reference:
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