Ebay offers National Geographic Epic Forts Science Kit for $13.99 (reg $39.99) with free shipping.

Product Description:
Kids will build the coolest forts ever with National Geographic Epic Forts!
This revolutionary fort system comes with Flex-Tech bendable connectors which make it easy to construct a variety of structures from domes to pyramids to rocket ships! Sturdy poles in two different lengths expand construction options and ensure strong builds. Plus, a variety of rigid connectors enhances the stability of structures and adds even more creative ways for kids to build!
The 70-piece set comes with easy-to-follow, step-by-step illustrated instructions that explain building basics, giving kids the confidence and experience they need to invent their own fort designs. The possibilities are truly endless once kids start to get creative!
Kids can use the included sheet clips to secure a fort covering from home and take imaginative play to a whole new level!
This fort kit also grows with your family. It’s great for younger kids that love make-believe play. It’s also perfect for older kids, offering them endless engineering challenges and creative ways to explore their inventiveness.
Get the National Geographic Epic Forts kit today!

• Contains: Does Not Contain Any of the 9 Major Allergens
• Suggested Age: 4 Years and Up
• CPSC Choking Hazard Warnings: Choking_hazard_small_parts
• Educational Focus: Engineering
• Includes: Instruction Guide
• Battery: No Battery Used