Honestly Carissa needs to revisit escape plans, she's getting close to the point of no return where anyone who rescues her is presumably going to consider her complicit in all of this and so she'd better either commit to getting out or commit to not getting out. She wants her headband first, though. She doesn't think that's just being greedy; the headband will maybe help her understand how the Yeerks see the world, and then she can decide if it's worth probably losing everything trying to stop them.
Going in and buying the most expensive kind of headband would be conspicuous but she can go to one shop and get the cheapest kind, and the ring of sustenance, and a cloak of resistance, and then go to another one and trade in the headband for a better one and buy a reasonable number of scrolls at each. The thought fixed loudly in her mind, in case anyone reads it, is that yes, she is a prisoner buying these on someone else's behalf, but the money is good and they're very dangerous and she doesn't recommend interfering unless they've got a way to Teleport her well out of here immediately.
The headband feels incredible. She studies some of the other magic items, too, until she thinks she might have an idea how to train into wondrous items if it comes up. Or do some kind of hybrid thing, no one does that but it's not obvious you couldn't...