Best Buy offers the Panasonic Viera Active Shutter 3D Glasses, model no. TY-ER3D4MU, for $19.99. (Amazon charges the same for Prime members.) Opt for in-store pickup to avoid the $3.99 shipping charge. That's the lowest price we could find by $19. Compatible with select Panasonic HDTVs (including DT50, GT50, ST50, UT50, VT50, WT50, and XT50 series models), these glasses feature active 3D technology and a rechargeable Li-ion battery that lasts up to 30 hours per charge.