Check Consumer Reports. They often show a "best buy" among their ratings because they know people aren't always going to pay top dollar. Their ratings will also help you find a good bargain on Craigslist if you know what's safe and sturdy.
Do you have a Freecycle group near you? You have to give something away first before you request an item, but after that you can request stuff you need. Often people would love for their baby items to find a new home and help out another family.
Check children's resale & consignment shops too. We have Children's Orchard - not sure what's around your area. You usually have to go often because some items fly out the door shortly after they are put on display, but you can call ahead and see if they have anything like what you're looking for.