I am a fan of their putty for fixes like this.  you can sculpt and mold it to whatever shape you want.  I used their waterweld putty to fix a plastic squirrel cage blower in a portable AC and the blower lasted another 5 years before it finally lost coolant but the blower still worked great.  

--Nathan, TX. Hire the lazy man. He may not do as much work but that's because he will find a better way.