Time is money. The magic roller derby fairy isn't going to help you. At some point girls on your team are going to have to invest time in fundraising if you want to make it work.

Do an NCAA bracket game. $10 buyin. Each gal on the team must get 10 people. Payout half the pot

I'm guessing people would rather just go in on one that doesn't have roller derby girls dipping their grubby little hands into the pot.

Roller zombie crawl. Do it at a school track or old emptish mall. Contestants get a belt and have to make it around the track. Make them wear flag football belts. When they lose them they Are out. Derby girls can wear rollerskates. If you can complete the course with any remaing flags you get a shirt or date with your roller derby girl of choice. Can do 35 to 50 for the race. Sell shirts also. Then give out wwinners shirts.