Missing the box at times

My cat is my cat is almost 9 months old. He is a very good cat is in good health and uses the litter box with no trouble. The only problem is that he some times takes care of business to close to the side and on a few occassions has missed and gets urine on the mat on the outside of the box.The box has one of the tops that snap on making it a few inches higher but he has still managed to miss one or two times.Keep in mind this has only happened a couple times since I have had him but I would like to know if anyone can recomend a higher or larger box and where I can get one other than the local pet store, is there some place on line? Thanks!

Petsmart sells a high-sided litterbox that's made by Rubbermaid. It has sides about 12 inches high, if I remember right. I think that should solve your problem.

My cat is a "high rise" urinator... he's also a BIG boy so I needed a box that gave him space inside with sides that were taller than him. I tried just about every box on the market today and he still managed to pee over the edge. Even the covered litterboxes were frustrating because he would pee against the lid and it would then drip down between the seams. ICK!

I finally ended up buying an extra large plastic storage bin for $6 at Wal-Mart and cut a hole on one end with a razor blade. It is the absoute BEST litterbox I have used! It's also the cheapest! For a litterbox this size I would have easily spent $15-$20 (or more). Plus, it gives me the option to have a covered or uncovered box by placing the lid on top or not. I highly recommend this option!