Townhomes are NOT known for having large back yards and the fact that most HOA's are responsible for maintenance of yards, they don't allow them. Currently, I do have a 3 bedroom townhome listed with a fenced back yard. Please check out my website: http://www.RaleighHomeSite.com
and look at my Featured listing at 4808 Landover Keep Place.
Is there a reason you are looking for a townhome vs. a single family home? If a larger fenced yard is the important item, you would be much better off searching for a single family home, plus HOA fees, if any at all, are much less on single family homes than townhomes which allows you to spend more on the home itself. Again, using my website, try the search engine on the main page. I think you may find it even better than the one on Trulia!!
If I can be of any assistance to you, please don't hesitate to ask.