Where can we buy chlorinated paraffin for lab application?
Sigma-Aldrich is a global supplier of purified chemicals for research users. 

They have a whole page of the haloalkane compounds they sell (in small quantities such as you desire).  You might be interested in compounds such as trichloropropane, pentachloroethane, etc.

A reason it might be difficult to get the higher-molecular weight compounds is that they are toxic and difficult to dispose of properly.  In the US, their use is subject to increasing regulatory requirements.