Yep find the part number for the Borla exhaust then search the interwebs for the best price. Gonna be around 400-600 new I believe. Used ones will pop up on the Buy Sell Trade section of this forum every now and then, that's how I got mine.
Oh and the Borla kit is from the flex pipe back and includes the resonator, muffler, mandrel bent tubing (2.5 inch), and all the hardware you need. Installation is a piece of cake. (Removal of stock exhaust can be a pain based on level of rust you have.)
Mine: 2006 Mazda3 s GT Hatch: 111k, Gray, Manual
Gone: 2002 SVT, #1654
Hers: 2010 Focus SES: 84k, Ebony, Auto, Moon and Tune