There are a number of places where one might be able to purchase a Suzuki quad bike. They can be purchased at most motorcycle or dirt bike stores. They can also be purchased used on websites such as Craigslist.
The short answer is no, if you only have a cbt you are restricted to 125cc with L plates. The 33hp limit applys if you take and pass your full test on a 125cc bike, after 2 years it automatically becomes an unlimited licence.