The original pic looks like the ones hospitals issue.
If you NEED one, your Doc, or the local Hospital should be able to issue you one, that's what the NHS is for.
If the second one is a WANT, rather than a need, visit your local Hospital and ask them where they get theirs. Contact the company and see if they'll sell you one. The hospital may even just give you one, as they "lose" a lot as many are not returned after injuries have mended.
If you see someone else using one, kick it out from under them, then pick it up and run away. Oh, sorry you can't. Walking stick racing anyone. (Before you all scream, this is not a serious proposal.)