A method that works for the person you have run out of ideas for.
Stop looking for an object they lack and look for a sentence they repeat. The gift that lands for someone with everything is almost never a better version of something they own — it is a specific reference to something they say, do or complain about.
Someone with everything has already solved their own problems with better versions of things. What they cannot buy for themselves is the experience of being noticed. A mug they use every morning delivers that reminder three hundred times a year; a nice object on a shelf delivers it once.

The other winner is the opposite extreme: something encountered once a year, with a date on it. An ornament is unpacked every December and carries the year it arrived. It accumulates rather than depreciating, which almost nothing else in this price range does.

A card sent for no occasion outperforms almost everything on this page and costs under ten dollars. There is no birthday to compare it to and no ritual it is fulfilling, which is exactly why it registers.

Cheap on purpose, specific on purpose, and used either daily or annually.
3$7.95