even though I have a BKT, and the BB products do contain sodiums, just not sodium chloride.
For a while i was thinking the BB products were stripping my BKT, then I just realized that my BKT brand (coppolla) is crappolla.
Anyway, to answer your question is a bit difficult because other than the BB products, all other products are for people who've had a BKT and they are significantly cheaper than the BB products, and not sure if they are BB safe( but probably will be). Many of the the BKT shampoos are not sulfate free....perhaps you can try SOFTLISS bkt products as an alternative. Softliss is made by the same company as the BB http://www.softliss.com/carrito/
. Their shampoo and conditioner duo is $29. Not sure if it's sulfate free though...since the BB is a softer treatment, you may want to only stick to Sulfate free shampoos...if that's the case you may want to bite the bullet and buy the BB products on ebay or amazon.
My beauty supply store sells a generic sodium chloride and sulfate free shampoo ( $9). Haven't tried it yet, but I'm sure if you search amazon you can find something similar there.