Obtaining sodium dithionite

[Fregrant]

Hi all!
I must to obtain sodium dithionite in a laboratory.
So, I need an example of obtaining sodium dithionite (Na2S2O4) from sodium bisulfite (NaHSO3) and zinc. Others ways (from sodium formiate, sodium amalgam, zinc, ash and SO2, etc.), unfortunately, are unacceptable for me.
Please help as quickly as possible.

[TheMasterMind]

how i would do it is obtain a solution of sodium hydrogen sulphite and sprinkle zinc powder into such solution and stir. sodium dithionate reacts with O2 in the air.

2 NaHSO3 + Zn ----> Na2S2O4 + Zn[OH]2