Above is an RV Toilet sold at Camping World. Click the photo for details. Browse the site for more options.
Shopping at Camping World allows you a couple different options. You can find the closest store in your area and shop there or you can order online.
About the only reason I can see for making the drive would be if you want them to install your toilet. If you plan to do it yourself then order online and save some money. That's how I do just about everything, but then I love doing things myself.
Not all RV's have plumbing. If you need a standard Porta Potti, we can help you there also.
All RV Toilets need chemicals to keep them clean. Below is a good selection.