Ever since I trashed my ankle again last year (see boot icon!) I've been meaning to get myself a pair of boots with some serious ankle support. Even at the best of times my left ankle flops sideways when I walk, while after two serious sprains in the past decade my right ankle aches pretty much constantly and minor sprains and subluxes are a weekly occurrence - welcome to life as a bendie! (OTOH I don't even get a full sublux, never mind a dislocation, so I'm comparatively lucky) I've been wearing hiking shoes/cross trainers for years, which suits my need for a supportive shoe, but they are very much a shoe, rather than anything that supports my ankles. I've used AFOs when I know I'm going to be on my feet a lot, but that's overkill most of the time and I wanted something between the two extremes. I hadn't come across anything to suit, but after a fortuitous websearch over Black Friday ('I wonder if anyone has any good offers?') I've ended up owning a pair of Kunzli Black Pro Plus boots (actually the older model shown slightly greyed out on that page).
They're actually designed for people with acute ankle injuries as an alternative to a cast or a walker boot, but the company website claims they're also suitable for chronic injuries, and I seem to have ended up with exactly what I've been looking for. The pair I've got are a little bit 'orthopaedic' looking from some angles - it varies between models, some are more obvious than others, but it's not as if I'm going to be out without either chair or crutches, so who am I fooling? The lateral support they give is precisely what I need - the heavily padded ankle has two built-in plastic support bars in an A-shape on either side. The A-bars make it almost impossible to roll your ankle sideways, while they're so heavily padded you can't actually feel the bars directly, it just feels like the entire shoe is supporting your ankle. Pointing your toe isn't as restricted, but the sole is near rigid, with a rocker shape to compensate.
The major caveat here is price, they're a handmade Swiss design that retails for around £230 normally (eep!), and I was lucky enough to find a pair on ebay for £60 (£75 when I first looked, which I ummed over, but the price had dropped when I checked back). I certainly wouldn't have risked buying them at full-price without trying them, and I'm not sure I could have persuaded myself to spend that much, but for the price I paid I definitely ended up with a bargain. There's a minor caveat on fit, the pair on ebay were a UK 9, my feet are 8 and 8.5, so I was pretty confident I'd be able to fit in them, but there's not a lot to spare on the left foot. I think that's mostly down to me, my feet are very high-arched and my big toes tend to push up as I walk (I must be one of the few people who regularly wears out the top of shoes not the bottom!) which likely means I'm a bit more sensitive to how much space there is at the toe than most people are, but there's a chance their sizing may be slightly on the small side.
(And a very minor caveat that they're quite a narrow sole, almost a centimetre narrower than my normal shoes and I half feel like I would be falling off them sideways but for the A-bars - but then my normal shoe is a hiking shoe and almost anything is going to be narrower by comparison! I think this is probably just a case of getting used to them)
Realistically that ebay find was a fluke and you're not going to find something like this in a high street shoe shop, but if your ankles have reached the point where you need some serious support and you don't want to progress to AFOs, then something like this may well be worth looking into - the applicable term seems to be 'stability boot', though using it as a search term seems to pick up the walker-boots as well.