Sexy question.
As far as I know, sodium bismuthide isn't stable enough. Bismuth hydride on its own decomposes at room temperature. You'll need decent packaging around it for any sort of application. But you already know that so... I can only guess why you're asking. Is it to see if I'd tell you what we keep in our sub-zero?
That said, are you interested in acquiring some raw bismuth while we're in Bolivia? We can split the bill. If you know a source, share.