Two part phone mount for camera tripod. Use standard 1/4 nut, insert it hot to fix it in the mount. Use one rubber band to make it work. You can glue 3 pieces of rubber band to both parts to hold the phone tighter.
Source model: https://cad.onshape.com/documents/d512c9dfaa820ce8d88532a8/w/2954ee61c0fc17947cf0edc6/e/e64fcb1aeb414f09a0257d58