When I do a Google search for packs or cells, the Voltaplex website is constantly in the top results. I have no experience with this company, but they do advertise a pretty decent warranty. It appears that packs are built-to-order, which I think is a nice and personal "just for you" touch. Also, their quote request form asks for some pretty detailed information regarding specs.
If you do decide to do business with Voltaplex, please report back here and share your experience. I have a generally positive impression from the website, but that of course is lacking any real-world testimonials.