How to cut Patio Pavers
You could probably rent a saw like this from your local hardware store.



They will usually have a diamond tipped masonry blade. You'll also want to make sure it's a wet saw or you keep the stones wet as you cut, as the dust from cutting concrete can make a real mess and be harmful to your health.

You may also be able to find a splitter like this.



The splitters produce far less dust and noise, and can usually be found cheaper than a saw (I found a couple on-line for a few hundred dollars).  However, splitters may not produce a perfectly clean cut. Splitters also come in pneumatic and hydraulic varieties, purchasing those might be out of the budget ($1000.00 and up) but might be available for rent at a reasonable price.