You can purchase them at hobby centers around town. If you want high primo trucks, that's where you need to be. IF you want something small, head on over to Walmart, they have a good selection in the toy section.
There are many places that you can buy a hand truck online. Two places that you could buy one online at Sears. Or even from Walmart online.
One may buy a used Ford F350 Super Duty truck from a local second hand car dealership or a friend who needs to get rid of such a truck. Cargurus offers some as well.
The collapsible hand truck is a great way to develop these items. The best thing to do is to try it before you buy it.
I think you should buy at least two drum hand trucks for your warehouse. This is because you may never know when you will have to use them. A drum hand truck could also save you lots of time.
One can buy a used Ram Dodge truck from local retailers that sell used automobiles. One can also buy a used Ram Dodge truck from the Dodge dealership.
One can purchase hand truck wheels at Amazon, Sears, HomeDepot, NorthernTool, ServiceCaster, Grainger, HarborFreight, Alibaba, etc. One must check also with the suppliers from China for hand truck wheels to get a cheaper price.
One can purchase a restored or second hand 1979 Ford truck online from sites such as Trade Trucks, Gumtree, Ford Trucks, Ford of West Memphis, Oodle, Old Ride and eBay.
Garbage truck toys can be bought both online and from numerous physical retail outlets. If one requires a new garbage truck toy one's best bet is to look at a toy store, but second-hand trucks can be bought much more cheaply from auction websites.
One can purchase a second-hand freight truck at Truck Paper, Commercial Truck Trader, Freight Line Trucks and Global Industrial. These types of trucks are also available at Auto Trader, Select Your Truck Deal and Harbor Freight.
Garbage trucks would be quite expensive to buy because they are an industrial truck and not accessable for just anyone to purchase. The least expensive way to buy one would be to find a second hand one that the town you live in is no longer wishing to use.
Personally, I would buy one that is lifted or have it professionally done. If you buy one already lifted, you don't run any risk of messing up your truck.
There are plenty of convertible hand trucks available for purchase, however, you may want to consider renting one instead as they are very expensive. Shop around for the best deals.