I bought the Vexplo adjustable pole mount fishing rod holder from Amazon to attach to my bike (NOT free). It is equally well suited for a regular freshwater fishing rod as well as a huge surf fishing pole. After reviewing other holders, I think this is the best setup I have seen so far! I mount it on my ebike, and it will work equally well on my mountain bike. Being able to spin to any angle means it will not collide and interfere with your other gear.
Affiliate link to holder: https://amzn.to/3MQKzIa
Affiliate link to M6 screws: https://amzn.to/3zsR7tK
