No need for wood. just take a metal pole and install in the clamps you currently have the antenna mounted. It should be long enough for the top to be just above the handrail. i’m guessing antenna length but the pole would probably be 0.75 - 1 m long. To the top of the pipe, clamp the antenna. Only issue, you will need a slightly longer antenna cable.
Remember the golden rule, antenna height is far more important than an extra dB or two of antenna gain. You need to get above all the obstacles and get a clear line of sight in all directions.
Nice photos by the way. Which city is the gateway located?