On the left-hand side of the artist’s profile page, you will also find a list of galleries who sell works by that artist. For example, on Dzama’s profile page, you can browse over a dozen galleries that sell his works.
To find the work you want, you may want to reach out to as many galleries as possible, and ask them if they have works in their backrooms that are similar to the piece you are looking for. Here’s an example of a message you could send: