A holder for removably attaching a portable electronic device to an elongate support such as a tray table latch on a seatback with a stowable tray table comprises a clamp frame, a spring compression lever slidably attached to the clamp frame, a flexible band for suspending the clamp frame from the elongate support and a self-centering clamp for gripping opposite sides of the elongate support. The holder may optionally include a device adapter for attaching a selected electronic device. Another embodiment comprises steps in a method for holding a portable electronic device against a seatback having a stowable seatback tray table.