Depending on which story and characters I’m writing for, they each have a different kit, that they’ve built up over time. But I’ll go with one that was pieced together by a character yet to make his appearance here at the Black Van, JC.
JC’s kit looks like a normal bookbag filled with clothes on top, like he’s going to the gym. Underneath his spare set of clothes, he has zip ties, a balaclava or ski mask (prefers the ski mask but the balaclava provides better coverage), electrical tape, a stun gun instead of a tazer, latex gloves, latex rubbers, lube, water, small spray bottle of household cleaner, box cutter/construction knife, screwdriver/bitdriver, gloves, small set of lockpicking tools if he doesn’t have a key or code to get in, spare cameras or phones for recording the fun (it’s for the Club, record the deed for the patron), toiletries, and shoe covers.
He prefers the stun gun over the tazer because it can be used multiple times. If he needs to scare someone from a distance, he will carry a gun, but prefers not to. Everything in his kit can be explained away except for the gun. If he gets stopped to or from a job, a quick look shows he was working out. The toiletries back that up, plus a couple sprays of Axe covers up the smell of sex. He can even explain away the rubbers and lube if needed, but not a gun in most places. The tools are basic ones everyone has, and lockpicks are in a computer tool case. He does IT stuff, so he can get away with it. And the electrical tape has better tensile strength than duct tape and leaves less of a mess. A lot of it can go a long way.
I’ve written other characters that had other stuff in their kits. Some used gym bags, others bookbags, one even used a toolbox when his cover to get in the house was as the cable man. One story had a man dress like a pizza guy, complete with delivery bag. Guess where his kit was.