Imidazole-1-sulfonyl azide HCl (CAS# 952234-36-5) is an efficient, inexpensive, and shelf-stable diazotransfer reagent.

It has proven to equal triflyl azide in its ability to act as a "diazo donor" in the conversion of both primary amines into azides and activated methylene substrates into diazo compounds.

Most importantly it is inexpensive, shelf-stable, and conveniently crystalline.

Goddard-Borger, et al. Org. Lett. 2007, 9(19), pp3797–3800.