You can get a new third party power adapter on eBay for about $20
http://www.ebay.com/sch/i.html?_nkw=macbook+power+adapter&_sacat=0&_sop=12&_dmpt =Apple_Laptops&_odkw=macbook+power+adapter&_osacat=111422&_trksid=p3286.c0.m270. l1313
Watch out for that first one listed. He has it for sale for only $9.99 but the shipping charge is $69.99.
Any new adapter will come with a 1 year limited hardware warranty when purchased from Apple at a retail store, through Apple Online, or through an Apple reseller.
In addition, the troubleshooting article for the Magsafe adapter, http://support.apple.com/kb/ts1713, as well as the article on properly disconnecting the Magsafe adapter from the computer, http://support.apple.com/kb/HT1453, and proper use of the adapter, http://support.apple.com/kb/HT1630, should keep it from having any strain relief issues.