proper flashes?? very heavy and expensive (£1000+) battery
on the cheap? as I would do..
YN flash, 100 quid, compatible battery pack, £20
4 x batteries and 8 x AA batteries (eneloop??) and a charger, 20 quid I think.
tripod £?? for each and softbox/brolly,
tent/ground pegs to hold it in place incase the wind picks up...priceless