I’ve never made a Herman piece to go with this rhyme as I have preferred imagination and my hands to show his size. You certainly could make your own Herman if you wanted to.

Each time you cycle through the rhyme shows Herman’s size with your finger. Start small and get larger. After he burps, he is tiny again.
I was sittin’ on my fencepost,
chewing my bugglegum chew gum loudly
Playin’ with my yo-yo! pretend to yo-yo
When along came Herman the worm.
And he was this big. show his size with fingers
And I said, “Herman? What happened?”
“I ate a grape.”
Apple…
Banana…
Watermelon…
Burped…