Use bamboo stakes and loosely applied garden ties to hold them up.
Bamboo stakes is about all you can do.
If there is some kind of horizontal bar near the lights you can use string, or as others suggested, bamboo stakes.
@ChittyChittyBangin uses poles for his monsters.
Mine are smaller and tied for the winds that get that area.
Tent dweller is staked out, too.
Ive bought 30 4 ft poles in the last 3 weeks 
@ChittyChittyBangin
Monsters
FEEL ALRIGHT HUH…
They wanted $2.38ea. at Menards…I took a 6’ 1x6 and ripped down 40 stakes…couple boards saved $90…crazy…