Lithium Nitride may prove to be a much simpler method for the home chemist then achiveing LiH or LiNH₂ to synthesis the Dimsyl ion. Li₃N is synthesized thru the direct combination of the elements just as LiH and LiNH₂ is yet obtaining dry Ammonia is next to impossible and im not so sure that heating Lithium and Hydrogen is such a great idea considering the big boom factor in the equation. However Nitrogen can be had for a fair price with ease. There are a couple methods for producing it and one that caught my attention recently was one where it was prepaired in mineral oil whose density lies between that of Lithium and Lithium Nitride and Nitrogen is feed into the mixture under high stirring. Since the reaction is exothermic the temperature can be controlled by the amount of Nitrogen introduced into solution. After completion of the reaction the Lithium Nitride sinks where the unreacted Lithium floats. You can also produce it by heating it in a N₂ atmosphere but for some reason this is said to produce an impure product.

Ok down to the chemistry of the reaction. Lithium Nitride is such a Powerful base its stronger the Alkali amides and Alkali hydrides like LiH. It is so powerful its able to deprotonate hydrogen itself givin this reaction according to wiki and quite a few other sources, Li₃N + 2H₂ = LiNH₂ + 2LiH. LiNH₂ reacts with DMSO to yeild LiDMSO and NH₃ and LiH yeilds LiDMSO and H₂. As you can see Lithium Nitride may prove to be an accessible reagent for the production of Dimsyl ions.