Going without food for a few days wont hurt him.
There is potential risk (as noted above) to using wild caught insects.
If you're worried about what to do if you run out of insects, the best and safest solution may be to start breeding something yourself.
That said, I breed plenty of insects, have several stores locally from which to buy, and yet I do still use wild caught insects. Not from a suburb or city area, but rather an organic farm in the country and a park/wilderness area.
But Im still knowingly running the risk of bringing home parasites to my chameleons. I have fecal tests done with some regularity and have enough money saved to ensure treatment costs are easily covered, if required. So far I've not had anything too serious result.
Also there is some risk a wild caught bug ate something that will stay in its system long enough to cause harm to my chameleons. I try to mitigate this by keeping and feeding the wc bugs for at least a day to clear anything in their guts. This does not entirely remove the risk.
For me, the perceived benefits of occassional use of certain wild caught bugs (different nutrients, chameleon interest/excitement) makes the risks worth it. But I mostly rely on / use bugs I breed myself, plus store bought crickets. There are lots of bugs you can breed easily, with little effort or cost.
I started with kingworms aka superworms. Extemely easy (if slow to get started) to breed, take up almost no room, no noise, no smell, extremely low cost to house and feed.
Roaches are a commonly suggested feeder insect you can breed yourself.