Colleges do host team and individual showcase events for softball and baseball.
Some are invite only and most in the Ohio, KY, WV, Indiana areas NAIA, JC or DIII for softball but if you search and are willing to travel you can find some decent 4 game weekend round robin format events or one day events hosted by a larger college or several colleges. 43ft-E-teams at one time is where a lot of the schools would post.
Most of these are fall/winter events that are also fundraisers for the colleges and can be combined with camps. Others may have tournament organizers (The Q sport / NFCA etc.) and most games played on a college campus like the one that used to be played at Winthrop university in SC in late August early September.
We would play in some smaller ones as well at 14+ hosted by colleges within a couple hours drive. The best ones was the Vernon Bibb memorial played at one of the Host Colleges in the Fall and the Keith Carver memorial Maysville KY late Summer where we played not only other travel teams but also against college teams or, teams made up of all college players in the KC open division. Now these were three day events with about 30 teams college/club participating. Back then Static, Doom, Force, Louisville Stunners and Louisville Sluggers is who we would see that also was at other events we played in.
ONU, Sinclair, Shawnee State, also held small round robin one day events we would get into with the travel or HS team from 2009-2014.
Remember, your teams coaches and players can make any event a showcase event with contacts and communication. 10/12 years ago our organization could get local small NAIA, DIII or JC college coaches out just to watch our teams practice...While there are not as many as 10 years ago I have heard of other organizations able to do the same thing.