Partsguy-
That is correct, you can only get them for their trucks, at least as far as I'm aware.
There are assemblers out there for the aftermarket as direct replacements for Lead Acid, but because the trucks were originally intended for Lead Acid, you may find some performance limitations with Lithium. It appears BYD has optimized their trucks for the Lithium battery perfomance.
This is ONLY to be used to report flooding, spam, advertising and problematic (harassing, abusive or crude) posts.