For what it’s worth, I saw your answer and was intrigued, though not yet convinced, by the argument there.
People who watch the home page will see when an answer has been added, removed, or edited to a question regardless of its age (unless the question is downvoted to oblivion, at which point it no longer shows up). That’s how I saw your answer.
The original asker will also be notified directly when someone adds/removes/changes an answer, and - if they are still active on the site - will often respond to new posts. In particular, they may notice and react to better answers by commenting and perhaps even changing their accepted answer to the new one.
Beyond that, the other suggestions GentlePurpleRain offered are applicable. Note that anyone with enough reputation can put a bounty on a question which tends to draw attention to the whole page, including any answers on it; while it’s usually used by someone other than an answerer to draw attention to a question or reward an exemplary answer, nothing says an answerer couldn’t use it to draw attention to the question themselves.
I do want to point out that if your goal in seeking attention for an old question is more about seeking reputation for a new answer, I would caution you to temper expectations. It’s not particularly common for old questions with already accepted answers to get a lot of fresh attention (the presumption, and often the reality, is that the asker considers the question solved and is unlikely to change their mind unless a truly novel and better answer is offered; and if it isn’t good enough for the asker it will tend to be ignored by other visitors). Chasing reputation isn’t ideal anyway, but if you’re trying to earn it, answering current questions is a much better bet. So, too, is asking a question of your own - or, even, suggesting edits to posts that can be improved.