do you have something to mount it to on the top? otherwise you need one of these:
http://www.platinumstages.com/NEW-St...ole_p_285.html
if you can mount it to something sturdy on the top you can buy a pole and just cut some slits down a few inches and bend the metal as a tab to screw it in. should cost under $100 total. heres a pic of the same type of pole on my party buses:
