What you can do is "construct" a longer head of hair; use firm hold gel, brush wet hair back into whatever you can get in a ponytail, spray the hair with lacquer, and then get one of those fake "buns"/hairpieces (they are circular, and loop around the base of the ponytail). Tuck the end of the "ponytail" under before you put the hairpiece on, a few hairpins, and you're good.
I think the hairthing we got cost us around 10 dollars, and in all the years we used it, nobody realized it was fake hair. It looked great. Hairbands, hair loose, was never allowed by our coach; we learned the technique from local synchro skaters who all used to do it so they would have identical hairstyles for comps.