You do have some excellent choices in this market: Ruger, the two popular Glocks (models 19 and 23), Kahr K9 and K40 which are all steel, Sig Sauer, Springfield Armory XD series, and the Smith and Wesson M&P series. All of these are either compact by design or make compact versions of their full sized guns. I prefer the .40S&W cartridge over the 9mm most always, but I do carry one of my 9's from time to time. With a good self defense load, this is an effective and proven caliber; shot placement and followup being your main concerns.
A good rule of thumb is to carry the most powerful caliber/gun combination you can with which you can consistently and effectively deliver rounds to target. If that is a .45ACP, .357 Sig, or .40S&W, so be it. If it happens to be a 9mm, then that is what you should use. The key is being able to be effective and deliberate with your weapon system and have confidence that you can use it consistently and confidently.
Gun shows are excellent vehicles for multiple and varied selections for you to handle and consider good candidates for a SD handgun. Take advantage of them. And generally the prices are below what you will find in local shops, though throwing a bone to your local shop(s) is always a good thing since you might want/need their services down the road.
Once you have narrowed your choice down to a few candidates, do as much research as you can on them. View videos and read reports/opinions/critiques, especially paying attention to any negatives. If you see a negative pattern developing, that is not preference or bias based, that may be a good indication to bypass that particular gun. Also remember that you can always make a few modifications or alterations to bring the gun more in line with your particular needs and desires. For example, many people complain about Glock triggers. These concerns are easy, simple, and very inexpensive to address to provide a significantly better trigger as you may already know. Just be careful when doing any modifications as you do NOT want to disrupt its reliability or safety.
So two fine examples of a compact pistol, since you are already comfortable and familiar with the Glock, would be the 19 and 23. If you are willing to go up slightly in size, the M&P Smith and Wesson in either 9mm or .40S&W is an excellent consideration with superb feel and hand fit.
Lots of good stuff out there.