I printed a handle that attaches to a pull rope for kids bikes.
The handle is designed so it will fit underneath the saddle of your bike.

You can also use it for other outdoor activities.
It is compatible with a pull rope from amazon, but other similar pull ropes will also work most likely.
Pullrope that I used: https://www.amazon.de/gp/aw/d/B0CMSNF557 (No affiliate link)

During printing make sure you align it laying flat on the bed to ensure maximum strength.
If you wanna be on the safe side, print it in PETG or ABS and with 100% infill.

I printed it in PLA with 50% infill and it is super sturdy.

Of course you use everything at your own risk.