I don’t know about music written specifically for 26 string electric harp (didn’t even know anyone made electric harps with only 26 strings).
Some music I would suggest that you could easily alter to fit on a 26 string harp and sound great on electric harp are some of Deborah Henson-Conant’s compositions such as New Blues, Natalina, and Nightingale.
Also highly recommend by me for this type of harp are the arrangements by Verlene Shermer in her two books Traditional Tunes With a Twist (vol I and II). These are traditional tunes arranged for lever harp with a Jazz twist to them that makes them very interesting, and which takes advantage of the unique tone of an electric harp.