Limited availability: Billy Andrusco is not a well-known artist, so his albums may not be widely available. This is especially true for his older albums, which may have been released in limited quantities.
Out of print: Some of Billy Andrusco's albums may have gone out of print. This means that they are no longer being produced, and any copies that are still available are likely to be sold out or very expensive.
Digital-only releases: Some artists choose to release their music only in digital format. This means that their albums are not available to purchase in physical formats, such as CDs or vinyl records.
Independent releases: Billy Andrusco may be an independent artist, which means that he may not have a major label backing him. This can make it difficult for his albums to be distributed to major retailers.
Lack of demand: If there is not enough demand for Billy Andrusco's albums, then retailers may be less likely to carry them. This is especially true for smaller, independent retailers.
You can try searching for Billy Andrusco's albums on online marketplaces, such as eBay or Discogs. You may also be able to find his albums at some independent record stores.