D'addario PW-AJL-01
Straplok Strap retainers acoustic

The D'Addario Cinch Fit Acoustic Guitar Strap Attachment is the quickest and easiest way to attach your strap to acoustic guitars without a jack output button. Jack knobs are a notorious source of frustration when it comes to attaching or detaching a guitar strap, and often require the strap to be modified for an ultimately unsuitable result. The CinchFit for Acoustic Guitar system wraps around the end of your strap, and its cord clip makes it very easy to attach and detach, taking advantage of the weight of the instrument to keep it firmly attached to the knob.
Note: the CinchFit system for acoustic guitars is designed for use with Fishman
Fishman and Switchcraft jack output knobs.