Greyson's decals are now in more than 50 stores in 20 states and his father, Matt MacLean, said retailers in other countries have shown an interest in the decals since last month's toy fair in New York.
The stickers let young builders customize their creations with signs, lettering and artwork and because they adhere to smooth surfaces through static electricity, they are removable and reusable.
The family fulfills Web site orders from a curtained-off area in their basement. The stickers come in three themes, metro, space and transport, and sell for $5.99 per set of 84 stickers.
"I can't even describe the feeling," Greyson said of his sticker invention. "You feel excited when you hear someone just ordered 15 of your product."
