Have ADHD but can't recommend a coach unfortunately.
Are you medicated? If not can you get medicated? It changed my life! Even if it just a short term thing to enable you to get scaffolding in place.
I think you really need to speak to work about it. Explain it is a executive function disorder and that you are looking for external support to help you manage it. Make a list of your main areas of struggle and start looking for solutions with them.
Can you give us an idea of what job you do? We might be able to make recommendations based on it.
I strongly recommend switching off email notifications if you can, check no more than twice a day at preset times. Have a morning routine for when you get it, laminate up a list of tasks for you to follow, it really helps for when you are overwhelmed and don't know where to start. If you can plan your week then plan the boring stuff for when you typically have more energy and tasks you find more interesting for when energy is typically lower. Could you effectively shut yourself away in a room for x hours a day/week, play some focus music through earphones (look at focus at will), again have a simple list laminated of how to deal with each task. I.e. emails delete/file/action/diarise with alarms including pre prep time alarmed now.
Put OHIO across the top of those lists, a reminder to Only Handle It Once.
Could you get of those pens/watches with a voice activated recording feature? You can then just activate it and record what has come into your head so you can do it later. Have a daily alarm to remind you to check the recordings and deal with them then!
It's really shit and I hope you find something more positive soon.