I don't think anyone makes a dna 20 device that's intended to be thrown away when the battery reaches the end of its life. I suspect all small ones with 1200 mAh capacity use the same battery that's in the Vaporshark dna, which is this one:
That means you can get replacements and they're cheap too (~$3.00) the only question is whether you have the skillz to replace 'em yourself.

That means you can get replacements and they're cheap too (~$3.00) the only question is whether you have the skillz to replace 'em yourself.