I desire to find similar music, such as the theme here.
That theme song is distinctly recognizable as Irish folk music. You should try listening to some jigs and reels (forms of Irish folk dancing music.) The music you shared is fronted by fiddle, which is very common, but you might also find some similar Irish folk fronted by flutes, whistles, accordions, or banjos. Here are some examples of fiddle-fronted Irish folk: Maudabawn Chapel, The Stone in the Field, and Paddy Fahy's Jig.