Frosini was among the best ever at writing music that "just sounds good," i.e., fits comfortably under an accordionist's hand and gives maximum sound for minimum fingering difficulty. I am envious of his ability to do that.
You don't want to miss the rest of Frosini's oeuvre: there are several dozen pieces, the largest and most complex and "classical-sounding" of which are the 3 rhapsodies.
If you are open to a moving a little farther toward classical, you may be interested in Nikolai Chaikin, who wrote extensively for Stradella-system accordion in the 40s and 50s --- and was obligated to write music accessible to the masses, not complicated experimental "Western formalism," by the Soviet system --- before the Russians got deeply into free bass. (And born in Kharkiv and studied in Kiev, so those of us outside Russia can call him "a Ukrainian composer" if it's politically expedient not to play Russian music right now.)
Here are links to his Toccata and his Humoresque, with score on screen: see also the two sonatas for solo bayan, and the concerto for bayan and full symphony orchestra.
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Books? Well, Frosini has been dead 70 years so he is out of copyright and can be freely downloaded --- everywhere in the world except the USA.