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
The best spot for finding retired or specific "Slime Rods" from older collections. Check the toy aisle near the Monster Trucks;
Look for these vintage 1990s models if you want the "classic" slime feel. Quick Shopping Tips hot wheels slime where to buy
These packs often include a small container of slime.