Check the toy aisle near the Monster Trucks; they often have exclusive sets.
Apps like Facebook Marketplace often have "bulk" lots of these for cheap. To help you find the exact set you're after: Do you prefer the vintage 90s Slime Rods ? What is your budget range ? hot wheels slime where to buy
I can find specific links and current prices once you let me know! Check the toy aisle near the Monster Trucks;