It sounds like you're doing a double french fold.
It's possible that you'll find templates on the websites of some larger printing firms and online print sites. Whether you'll find one that fits your particular need is another question. When it comes to less-common items like this, templates are also far less common. The foldfactory site is an excellent professional resource (not free) for any kind of fold template on any kind of foldable stock.
Your best bet is to fold an 11x17 sheet the way you want it to end up, sketch what should be on each panel (which will help you orient the layout correctly) and measure. In most cases of complex folds, I do them from scratch in just this way.
Once you have your dummy, take it to the printer and go over paper types and your dimensions to avoid problems. Follow your printer's advice. Don't be surprised if the job turns out to be a lot more expensive than you thought, because of the bindery work.