Here is the original pattern:
Making it to fit a 3 year old - 5? (25 inch chest)
Cast on 114 sts (57 sts per side). Place marker. Join in the round.
Knit in 1x1 rib for 8 rnds. Place second marker after 57 sts.
Purl one round (hem turning round).
Start knitting, and start of row 1 for Chart A
Attach pocket at the rnd 10 (rnds are counted after the hem turning round) as follows:
Knit row 10 of ChartA, knit 6 sts, don't break the working yarn. With a new ball of yarn attached knit next 30 sts - those are the start of the pocket. Rest of the pocket is knitted like in the original design for 20 rows (row 4 is like row 6&8, ie not a decrease one like in the original). Pocket goes from 30 sts to 20 sts.