Where to get line cords

[Gilas]

Ok now that I am officially addicted to this hobby, btw I blame you all  . I have a question.  Where is the best place to get line cords at?  Looking for just bulk black rubber modular cords so that I can hook some of these up.  I have purchased a couple of the cloth ones through oldphoneworks but for just plain rubber where is the best place to go.  Are they easy enough to do yourself, if so any tips from the pros?  Any help would be greatly appreciated. 

Thanks

Mike