I have researched the plasma thrower but have no idea, on how to make deuterium gas. Are also in a Bob's run. Second thing i even click on the gas in FNEI but no recipe show up. Putting some images that might give u a hint on how to help :) Also after putting the second link i saw i didn't have the electrolyser
You should be able to make heavy water with the electric boiler and then electrolyse it with bob's or angel's boiler (depending on which you have installed). If you can't, then that's a bug.