This problem is one facing anyone who's been out of work, then finds a job and needs to equip themselves with the tools of their trade, whether that's a suit for the office, a bag of spanners, or musical instruments.

Is there any assistance available in your area for people in that situation? This might be from government or charities. You'd probably have to demonstrate that this can be turned into a way of making a long-term living, and the difficulty is that some people don't take being a musician seriously, although it's really no different from other freelance work.

Have you asked the other band members to lend you the money - you've got them the gig, so surely it's in their interests? If you can't equip yourself, there's no gig and no work for them.