They exist but I don't think they have any relationship with Beretta what-so-ever. http://www.gunbroker.com/Auction/ViewItem.aspx?Item=303966676 or http://www.gunsamerica.com/blog/the-kel-tec-sub-2000/
@MilOperator -
No relationship with Beretta...different models accept either Glock or Beretta or S&W pistol magazines...looking for the Beretta model...thanks for sharing the link.