I came up with this idea because I couldn't decide if I liked this jacket belted or not. It's not fancy, but it works and the loops are hidden when not in use.
Tools/Supplies needed: embroidery thread in a color that blends with jacket fabric, embroidery needle or needle with eye large enough to fit 2 strands of the thread.
1. Cut 4 strands of embroidery thread. The length will depend on the thickness of the belt. Cut enough length to wrap loosely around the belt and also tie a knot in one end. There will be 2 threads per loop.
2. Pull 2 strands through the needle.
3. Find the waist-line of the jacket at side seam and loop the threads from inside, outside and back inside--make the stitch small so it is less noticeable when retracted. Tie the 4 ends in a knot inside the jacket--leaving the large loops on the outside of the jacket. Use a dowel/glass/whatever that is the same diameter as the belt if it's easier. Repeat on the other side.
To retract the belt, pull at knot until the threads are flat against the jacket fabric on the outside. To use loops, use a small hook to grab both threads and pull them out (on each side.)
note: I will add a detail photo of the loops in the near future.