Vernier DFS Bracket
Vernier includes a sheet metal bracket to mount a force sensor to a dynamics track as part of its Bumper Launcher Kit ($89). The kit comes with a variety of attachments for elastic and inelastic collisions. If you just want to do basic elastic collisions using a hoop bumper, you can purchase replacement hoops (2 for $15) and use this bracket to position you force sensor.
Printing this bracket is pretty straight forward. I use a medium setting and 35% fill, which took about 4 hrs to print. To mount the bracket to the track, I used 1/4-20 x .5" bolt and a 1/4" square nut. I used a plain washer to prevent the bolt from bottoming out on the track. To mount the sensor I chose a 1/4-20 x .5" washer faced thumb screw to make it easier to get on and off for calibration.
Original Vernier Bracket
3D Printed Version