Walmart offers the Plastic Sand Art Bottle with Cork 24-Pack, model no. TZ-YW-085, for $12.88. Opt for in-store pickup to avoid the $4.97 shipping charge. That's the lowest price we could find by $10. This 24 bottle pack includes all necessary cork stoppers.
Target offers the Up & Up Broadline Markers 10-Pack for 74 cents. Opt for in-store pickup to dodge the $5.38 shipping fee. That's tied with last month's mention as the lowest price we've seen. (It's a current price low by about a buck.)
Target offers the Crayola 24-Count Washable Watercolor Painting Kit, model no. 53-0524, for $3.99. (Amazon charges the same as an add-on item, with free shipping for Prime members for purchases over $25.) Opt in-store pickup to avoid the $5.12 shipping charge. That's the lowest price we could find by $2. It includes a paintbrush.