One of the problems of being avant garde in anything is that you find yourself out there all alone with not much backup. With the popularity of the instrument catching on at last, Bass VI strings are finally becoming at least somewhat available as opposed to evoking nothing but weird or clueless glances from the guy behind the counter when you ask for some.
Selection is still a bit of an issue but more and more custom string manufacturers are starting to offer Bass VI packages. A few of the really ambitious producers are even branching out into single string sales, which will allow you to customize your strings to suit your own particular tastes.
With more players using the Bass VI and more manufacturers producing strings to order, it is only a matter of time before these items become as common as any other sort of strings on the shelf.