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We all need them. Come on, manufacturers.
Still have a big hole in the top though!
You could easily make them snug, or fit a cuff like dry suits have. Or just make waterproof riding trousers that fit over.
It's less about keeping rain and water out, more allowing you to wade through the deep mud you get at certain points in the trail without your boots filling up. Even winter boots don't keep it all out.
I hate wellies!
So its a no from me.
Why not make your own? I once modified a pair of Karrimor boots. I expect the same could be done to wellies!

What if............flat pedals existed
Knee length sealskins do the same job & keep your feet warmer.
Northwave raptors and https://www.gripgrab.com/pages/cyclingaiter work a treat.
How deep are these puddles......
Is it wellies or waders you need ?
My old man winters keep any puddle im willing to risk riding through in winter out.
Whilst at Poly-versity I rode with the MTB team and a bloke there wore army boots with flats for a CX race. I rode with clips and straps. I came mid field and he placed considerably higher than me. He'd have probably won with SPD 'paras'.
Northwave raptors and https://www.gripgrab.com/pages/cyclingaiter work a treat.
I remember years ago (12+ years) on this forum someone recommending diving dry suit wrist seal cones to do the same job. Worked fairly well.
http://www.seaskin.co.uk/acatalog/Wrist-Seals-Cone-Standard--Pair--Spare-Part--WRISTSEALSCONE.html