It would be most helpful to measure or look up the
power consumption of your
LED tape. They do vary somewhat depending on how many LEDs per
meter,
etc.
One option might be a
power drill battery
system coupled to a DC-DC converter. Quick chargers and batteries are readily available. A 4 Ah 18V battery pack (or 20V, which is exactly the same thing after the marketing department gets through with it) stores 72 Wh of energy. If required for the full hour and a half, that would mean a maximum of about 40W of
LED tape after accounting for DC-DC converter losses
etc., and I'd rather have less than that.
Call it 3A at 12V maybe. Obviously shorter duty cycles mean larger currents could be available, as would being able to change the batteries.
DC-DC converter modules are available in various sizes and capabilities from many places, including Amazon. Oversizing them is not a bad idea, particularly for cheap import units of unknown provenance, as some are rather optimistically specified. Doing some good testing before the show is of course also a very good idea, and it would not hurt to have a spare or two available.
A simpler pre-built variant is one of the inverters powered by tool batteries that are available. Ryobi has a neat looking pure
sine wave inverter
unit for their 40V battery
system available from Home Depot that I think is particularly attractive, as it's not unreasonably priced and being pure
sine wave output there are no worries about powering most anything within its
power rating. Many inverters are "modified
sine wave" which really means a sort of bipolar
square wave output that can cause electrical/RF noise and that doesn't work (well) for a few devices.
Car batteries aren't super pricey, in my opinion, but they are heavy and battery acid can cause all sorts of difficulties and poses some
safety hazards on its own. Most car batteries are not at all designed for deep discharge, either; a trolling motor battery is somewhat better for that sort of usage (and a golf cart battery setup even better, though less convenient since you'd need two of the common GC2 golf cart batteries to get 12V...and that gets pretty heavy and large).