One can also enlarge the small negative under the enlarger onto lith film which will produce a film positive and then contact print this film onto another sheet to produce a negative. Many years ago I used to do this.
Now I enlarge to a sheet of x-ray duplicating film. Kodak used to make a terrific duplicating sheet film but it is no longer available. I bought a box of 8x10 x-ray duplicating film on ebay. Photo Warehouse, an APUG sponsor also carries duplication film in various sizes.