You are asking for fine grain in a 20X enlargement (I assume from the square format that you are coming from 2-1/4 square negatives). Although such enlargements are usually viewed at a distance that makes the grain of something like Tri-X unnoticeable, your post suggests that such grain is undesirable to you. That leaves only the very fine grain films. Pan-F is probably the most available, and it works well in a variety of developers. Xtol would be the first that comes to mind. There are other very fine grain films available that may deserve attention, such as Adox CMS II, but they may be hard to find. They may also require special developers.

From your post, I assume you are using ink jet printing (which is a quite different thing than carbon printing). The digital process can do a great deal to hide the graininess in a print, so it might be worthwhile to try a large print with your existing film and see how it looks. The Delta films have quite fine grain if developed properly in the recommended developer.