Start with ethyl cyanoacetate convert it into hydrazide by reacting it with hydrazine hydrate in ethanol under warming  condition at 70 deg. centigrade  then diazotise hydrazide with NaNO2 in HCl at zero deg. centigrade to get azide.

This compound is a liquid. There is a synthetic procedure: 

https://www.researchgate.net/publication/244769776_Organic_Azides_3_Ultrasound_Synthesis_of_Propargyl_Azide_Azidoacetonitrile_and_Primary_Allylic_Azides

using water as a solvent and ether extraction. I  remind you that this compound is a mighty and sensitive explosive and, besides, quite toxic. I would suggest not to prepare more than 500 mg pro run, and always use plastic safety shield and good ventilation.

Article Organic Azides. 3. Ultrasound Synthesis of Propargyl Azide, ...