Hi Edam welcome to the forum.
I must admit it is something I have never worn.
I have seen ankle gaiters worn to keep the dust out of mainly hiking shoes if walking a lot of gritty paths or scree. They should be OK as they don't come over the calf.
We don't have gorse or brambles here in Shetland so I do not need them.
I have thought about it for deep snow but that is so rare now.
I always thought they wouldn't add anything except extra heat, which might not help with feet blisters ultimately.
I do a lot of heather walking and rely on my trousers keeping the damp out of my boots.
I found this site but they are still 4 Cm to narrow
https://blog.cherrytreecountryclothing.com/gaiters-big-calves/Have you tried to contact Military outlets eg.
https://www.military1st.co.uk/footwear/gaitersI see RAB does stretch gaiters. you would need to contact them and see how suitable they are for you.
https://rab.equipment/uk/accessories-equipment/gaitersthey cant be too complicated to widen is this something a seamstress could help with?