I use a monopod a lot.
For birding, I have used the Lensmaster RH-M2 (an equivalent to the Wimberley, which appears to be no longer available). It was just under £150 so a lot cheaper than the Wimberley but works the same way.
The Wimberly got a very good reviews from Steve Perry.
I found it awkward to use because the camera/lens weight is offset from the centre line of the monopod, This means you end up, or at least I did, using the monopod at slight angle, which I never got used to. It also, of course only works if a lens has a tripod collar, or with an L bracket on the camera.
I also have the Manfrotto head described by
@tijuana taxi but found it impossible to get the right tension between it being easy to tilt and it feeling sloppy. But a better quality head of similar design would seem a good price/function compromise.
My Acratech Panoramic head (in the long lens version) would be a great head for a monopod
https://www.acratech.net/tripod-heads/long-lens-heads/long-lens-head/. It's pricey but there are several lower cost equivalents from people like Leofoto.
Although, people say there is no need for a ball head on. monopod, for "general" use I disagree and my main monopod heads are ether a the FLM 32
FLM CB-32 FB tripod head for photography.
english.flm-gmbh.de
or
the Novoflex Magicball "Free"
Novoflex create premium, precision engineered, professional photography equipment including lens adapters, macro bellows, ball heads, tripods and more.
novoflex.co.uk
For general use I find it the most stable approach is to make sure the monopod stays vertical and use the ball head to adjust vertical and horizontal tilt. But also, sometimes I feel it useful to "jam" the monopod at an odd angle and the ballhead lets me fully adjust the camera position.
For birding this doesn't work so well as a loose ball head (even one with adjustable friction), while following a flying bird tends to end up all over the place and is difficult to use. The Novoflex head is, for me, the best all round solution, good for general photography and good for birds.
At the moment the FLM lives on my general purpose monopod, and the Novoflex on my heavier birding monopod.
If you would like to try out the Lensmaster head to see how you get on with it, I would happily pop it in the post. It's just sitting here doing nothing. I keep on meaning to give it another try, but never get round to it. If interested feel free to open a personal conversation.