You will need: 

Helmet
Sports stretch pants and matching shirt (get the colors to match your favorite team)
Knee pads
Padding for shoulders (soft foam, small pillows, or lots of paper towels formed to fit)
White knee socks
Tennis shoes

Instructions

A.  Dress your child in his stretch pants and matching shirt. 

B.  Stuff the shoulder padding under his shirt

C.  Put the white knee socks on and the tennis shoes.

D. Place the helmet on (make sure he can see good, if not he can omit the helmet and just wear a baseball style hat that could even have his teams emblem on it)