I couldn't find a brochure template, but I did find a template on how to make one in Illustrator. Err, can't link since I don't have enough posts.
Almost all of the online printing services offer those templates. You can download them as ai, psd or eps.
Call the print shop that you're going to use, and ask them for the exact size (and also ask about bleed). Also ask about the how it will be folded - depending on the weight of the paper, and the fold, you may need to make one of the panels a couple of mm smaller.
Are you using InDesign or Illustrator? Oh Illustrator! Just to make sure, I got both for you, InDesign (http)://www.adobe.com/cfusion/exchange/index.cfm?event=extensionDetail&extid=1046393 Illustrator (http)://www.designfreebies.org/design-templates/illustrator-templates/free-illustrator-templates-generic-tri-fold-brochures/ Good luck mate!
Need a Corporate Tri Fold Brochure Template Design. It’s a Corporate Tri Fold Brochure Template Design for Any types of companies. It is made by simple shapes Although looks very professional. Easy to modify, change colors, dimensions, get different combinations to suit the feel of your event. http://graphicsdesignator.com/corporate-tri-fold-brochure-template-design/ Features : 300 DPI, CMYK Color Mode, Print Ready File, Well Customized Layered PSD File, Size 11.69”x8.27” (0.125 bleeds each side), Tri-Fold Photos in the preview image are only for display purposes and are not included.