Here is an "Inlatable Hammer".
Might they mean an Inflatable Hammer? Yes, but the typeo got all the way into production so inlatable it is. Appropriatly the package features Amy known for her piko piko hammer, however this isn't a prop from the game. Looking at the top it seems it may have the image from the package on the hammer head part & likely some decorative handle that's also inflatable. It is 36 inches long.
This would have been cool to have an actual real piko piko modeled after Amy's in the games...but this one's a good start with fun modern art and a good big size.