Tenergy via Amazon offers its Tenergy Odev Dynamo Lantern STEM Building Toy for $14.99. Coupon code "GXJ7QQ33" cuts that to $8.99. Plus, Prime members bag free shipping. That's the lowest price we could find by $6, although it was a buck less in July. It allows kids to build a hand-cranked generator which powers a light bulb. Deal ends December 9.