Monopods are infuriatingly underestimated in their sheer usefulness.
You can almost wrap your entire upper body around the camera/long lens when it's attached and so makes for quite a solid platform. Unlike a tripod, which is rigid and you have to constantly tighten/loosen, often many awkward knobs just to alter a little, the monopod-clad camera is fluid and moves with you - and the subject.
In my occasional bird photography, in a hide, the 'pod takes all the weight (3kg) of my D700 and Nikkor 80-400 vr zoom but I can scan around whilst looking through the viewfinder, firing as I want and not get tired. Relaxed snapper equals better photos!
For vertical shots, you can prop the shaft against a tree, even the pillar inside of a Church (when no-one's looking!) at right angles. The chunky rubber foot having excellent 'grip'. Consider bigger, heavier faster lenses (if you have one) that come with a tripod collar, this way you can loosen the collar and rotate the camera to a vertical position, as the tripod mount attaches to the collar, not the camera.
A previous monopod (lost at a Stonehenge solstice) helped me once clamber down a scree slope in Cornwall, giving ME support! You can also hoist the whole lot above your head with the camera on time exposure for a makeshift aerial shot....looks ludicrous, isn't recommended in high winds but is undoubtedly effective....
This Manfrotto model represents fair value, is of very good, solid quality, with positively chunky levers and is from a praised and reputable manufacturer. It's an effectively straightforward piece of kit with which you can't go far wrong.