I know this thread is from last year but I'm just findng it now.
I don't knit or crochet, but I love to cross-stitch. I typically buy the $20-$40 kits (either on sale, or with a coupon) from Michaels or JoAnn's. It's easy to carry around and to do backstage or in the booth - a lot of crafts (I also paint, for instance) either require room to spread out, lots of materials, are potentially messy (I'd hate to have paint get on a costume!) or are difficult to start and stop. I've always been scared that with knitting if I have to put down my needles all the stitches will fall off and/or I'll lose count!
Also, headlamps are the best things in the world! I used to think it was too dark to do anything backstage (and my arm got tired of holding a flashlight over my book), and then I discovered headlamps and haven't looked back. Not only are they fabulous during quick changes where you want to use both your hands AND be able to see the tiny little button/snap/clasp clearly, but also for crafting backstage during downtime. I have one that tilts, so I usually keep it tilted down (and keep it off when I'm not using it) so that I don't blind anyone who looks at me.