Amazon offers its Amazon Prime members Spyro's Adventure Flameslinger Character Pack for $7.99 with free shipping. (Non-members can spend $25 or more to qualify for free shipping; otherwise, shipping costs $4.98.) That's the lowest total price we could find by $18. It is compatible with PlayStation 3, Xbox 360, Nintendo Wii, PC, Mac, and other platforms. It requires the game and the Portal of Power to work.

Amazon Prime membership is $79 per year; however, Prime is free for college students for six months, and free for parents and caregivers for three months. (Note that currently there's a waitlist for Amazon Mom.)