New England Biolabs provides many products useful for working with miRNA and siRNA.
RNA Ligases catalyze the ligation of nucleic acids through the formation of a 3'→5' phosphodiester bond. Substrates of these ligases include single-and double-stranded RNA and DNA, as well as dinucleoside pyrophosphates.
RNA ligases are routinely used for cloning and characterization of small RNAs. NEB supplies kits (NEB #E7330, NEB #E6120, NEB #E6160) containing adaptors, primers, enzymes and buffers that are ideal to convert small RNA into cDNA libraries for next-generation sequencing.