My sister uses a neti pot and here's a link to a website that sells them, but you don't really need one.
Neti pot resource
A neti pot will probably cost $15-20 or more for a stainless steel version and they're sometimes hard to find. Plus you have to keep them clean.
You can easily rinse your sinuses in a more natural way using the palm of your hand and a little salt & water. A doctor recommended this to me and I do this sinus cleansing when I'm ill. Mix about 1/2 cup of warm water with a scant 1/4 tsp salt (as you would for a mild salt water gargle). Cup the palm of your hand and pour a tablespoon's worth of the mix in the natural cup of your hand. Take a deep breath, let it out and then suck that up one of your nostrils, while pinching the other side (I just press mine to the side of my palm... it works perfectly). It will feel weird, like when you're swimming and get water up your nose. The water will drain down your throat or you can spit it out. Repeat with the other nostril. Then repeat in each nostril a couple more times. When you're sick, you may want to do this two or three times a day.
Once you get the hang of this, you can do it all in just a couple of minutes. It is good for your sinuses and will clear them dramatically. The salt is a natural inhibitor for bacteria & viruses, too. If you live near the beach, you can do a similar thing with a shell & clean seawater... if you dare.