Any k frame S&W with a 4 inch barrel or less will work. I look for used S&Ws. Look for shooter grade guns. 38 specials that were used but not abused are often the best deals. A model 17 or 18 is worth paying extra for. You make the money back in ammo savings. Don’t forget a steel framed j frame or a 43C in .22lr as a trainer. Dry fire is king for cheap practice.