There is no specific requirement but aids recommended by an OT will carry a lot more weight than those purchased by the claimant, it just means that you have to work a lot harder when you describe your issues.
With specific reference to the chair, whilst there is Case Law covering this area, chairs and beds are not usually considered to be aids as many healthy people will use these to help them dress. You need to make it clear that the absolute only way that you can dress is with the use of a specific chair.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems