Amazon is a great resource for ordering leg elevation wedges. That's how I found the Lounge Doctor in the first place. Once you know the name of a wedge you can search for that brand and maybe find it cheaper on their own website. Or maybe through Walmart.com.
Also consider local medical supply stores. Call to find out if they have leg elevation wedges. They'll have less selection, and you will have to go to the store to see the product, but the plus is you can bring it straight home with you if you like it.