I think it may be fairly difficult to find zinc powder/dust since I have the feeling that it tends to oxidise pretty vigorously. It's pretty much like you cannot usually buy sodium and potassium dust for the exact same reasons, you just mix with water and see some pretty violent reaction.

What you want is basically a strong reducing agent, i.e. something that will reduce your dimethyl N-oxide back to dimethyl. What I can suggest is sodium nitrite and sodium metabisulfite (aka disodium bisulphite or simply sodium bisulfite), both strong reducing agents and available around me (they are also used as food preservatives)

Now, you just need to know redox potentials of these NaNO2 or Na2S2O5 as well as the redox potential of DMT-N oxide to see whether the reduction will work.

Any good chemists around to shed some light into it? (my guess is that it would work)