You can find cheap pickup trucks at auctions. When cars a repossessed or taken by the cops they go up at auction. You can bid on these trucks and get a good price for them.
When people have things to sale they often go to eBay. There they can find just about anything. People do sell pickup trucks on eBay buy they may not be cheap.
You can check for second hand pickup trucks on craigslist.com people are always on there selling trucks for really cheap. Just make sure you don't fall victim to some of the scams on there.
It depends on where you are located. I would suggest going to any nearby dealer will probably be your best chance of finding small pickup trucks. Any of the larger dealerships will have many of the same kind of trucks for someone to buy or lease.
You can buy cheap pickup trucks in local car dealership shops. You can also try online advertising sites. They always have some pickups for sale there.
You can buy relatively cheap trucks on eBay. The previous owner decides what the sarting price is, and then other people bid on what the owner has for sale. This means that you can find the same item for a different price on the site.
A good resource for researching and purchasing new and used pick up trucks is http://www.pickuptrucks.com/. There are also trucks available here for under $5000.00, http://autos.aol.com/gallery/used-car-lot/.
There are plenty of websites like www.pickuptrucks.com or www.cargurus.com or www.commercialtrucktrader.com or www.autotrader.com where one could buy pickup trucks.
You can find used pickup trucks on the used section of Pickuptrucks.com, http://www.pickuptrucks.com/html/classifieds/new-and-used-pickups-for-sale.html. You could also put a "wanted" ad on craigslist.org to find an inexpensive pickup truck.
http://ocala4sale.com/transportation/used-trucks-import.php has some listed sometimes. Or you can try ebay motors.
You can find diesel pickup trucks at many of the car dealerships. Sometimes you may have to order them as they may not necessarily be available on the site.
There are a number of used car dealerships in the Ontario area, visiting one or two of these that specialize in trucks and SUVs would probably be a good place to start. Also, looking in your local classifieds might also be a great place to find a cheap pickup truck!