Woot offers The Doorhickey: Hands-Free Handle for Sliding Glass Doors - Set of Two for $13.65 (orig. $29.99). Free shipping for Prime Members.

Product Description:
The Doorhickey instantly suctions to the clean glass of your sliding door. When your hands are full, you can open and close it easily with your elbow, shoulder, hip, or whatever. It's also an assistive device for those with limited hand mobility. 

• The smart, safe, hands-free way to slide glass doors!
• STRONG vacuum suction for a Herculean hold!
• No assembly required!
• Set of two: one for the inside and one for the outside!