You can get a clamp heat lamp with reflector at
Walmart in their lighting section, near the extension cords and shop lights, and can buy a brooder bulb (at least 125 watts) from Lowes in the lightbulb section, or at your local farm store- get red if you can so they chicks play nicer with each other. If you're desperate and can't find anything, you can go to a pet store and find heat bulbs and lamps in the reptile section. Just make sure you have a thermometer to keep the babies at 90-95 degrees the first week and drop the temp by raising the lamp every week by 5 degrees.
I have a huge 100 gallon 3 ft long rubbermaid which I cover the top with 20 inch wide, 4 ft long wire rubbermaid closet shelving/garage wire shelving, and the heat lamp goes directly on it. If it's really cold, I cover half of the wire shelf with a towel to reduce drafts- keeping it well away from the lamp. It's better than getting cut up by the hardware cloth! The spacing between the wires on the shelving I use is too small for a mouse to crawl through, or a snake!
I've kept mine in the house for the first 2 weeks in the brooder box and use paper towels for the first week, then pine shavings after that first week to cut down the smell. I usually elevate their waterer and feeder on a large flat 1 or 2 inch brick to keep them from getting buried in the shavings by happy chicks. But by week 3, they start getting smelly- even with frequent litter changes, so they go in the garage with the heat lamp and pine shavings, with a radiator space heater in the garage.
Here's a pic of mine. I have 2 heat lamps in case a bulb burns out.