I'm assuming this is about the Bamm Bamm inflatable punching toy, one of the Punch-Me character series, and not an actual punching bag used by boxers for training. I haven't been able to pinpoint which company made these. Some were made exclusively for Sears. The 1970 Wishbook listed Bamm Bamm for $1.97, because he was shorter than most of the other characters. The Punch-Me toys were made of vinyl, with the bottom filled with sand to keep them upright. It is odd, that later in the 1970s, the teenage Bamm Bamm image wasn't used. The makers stuck with the toddler Bamm Bamm image, until discontinued around 1978.

Found image of a box for a Bamm-Bamm Punch-O bag by Coleco from 1968. Bag stood 34 inches tall and sand had to be filled into the bottom to keep it upright.

Found a colorful page with character Punch-Me upright inflatable toys. Along with Bamm Bamm, were King Kong (Rankin-Bass cartoon), Flipper, Dennis the Menace, Batman, Bozo, Popeye and Tarzan. These were in the 1968 Sears toy catalog, courtesy of Wishbook Web. Prices ranged from $2 to $4 and change.