You need 3 parts: a ~40 inch selfie stick, a tiny photographic tripod and a gopro style bike mount.
For whatever reason, 36 inch sticks are easier to find (you might already own one): those work as well but the resulting loop will look a bit ovalized. Make sure your selfie-stick has a photographic screw at the bottom so that you can eventually connect it to a tripod.
The tripod I use is intentionally as small as possible. It won’t sustain winds but its very small to carry around. For me it works perfectly but you might prefer getting a slightly larger one if you intend to operate under wind conditions (they cost the same).
In order to allow the loop to be flat on its plane, the two go-pro mounts (the one at the top and the one at the bottom) need to be perpendicular to one another when the stick is fully extended.
All done. The loop is finished and ready to be used.
I hope you will enjoy using it as much as I do. Good DX!