Years ago, I had a close friend who was hired to play guitar in a campy, retro '50s rock & roll band (think: Sha Na Na). He had really long hair at the time, down to mid-back, and of course this was not appopriate for the era the band was trying to recreate. In other words, they wanted him to look like a 1950s "greaser". As with you, cutting it off wasn't an option, so before every show he would get his girlfriend (or me) to put it in a tight braid and tuck it into the back of his shirt. Then he would slick the front back into a kind of greasy pompadour with some industrial-strength hair product and presto! Instant 50s hairdo.
Mind you, all he really had to do was stand still on stage and play guitar (most of the antics being performed by the lead singers), which means that it was unlikely his braid would pop out. You, of course, would be moving about more, turning your head, etc. so this may not work for long, but you could try it out for, say, an afternoon and see how it goes. (skip the greasy pompadour, though!)
Just a thought...
Time flies like an arrow. Fruit flies like a banana.