I don't know of any site that lists demo days since they are so unique to an individual location and typically sponsored by a golf club or a retailer. I have only found them through local advertising. We had a demo day last month at my club so I know they still happen.

Demo days aren’t common with Titleist. Similar to car sales, they tend to generate “tire kickers”, not sales.
I’m getting notifications from Titleist for TT fittings at clubs up to 50 miles from home. I also am on the mailing lists for about 5 clubs besides my current club. A couple have also notified me of events they are sponsoring with Titleist for TT fittings.
You can check with local pro shops to put you on the mailing lists for events open to the public. Even at private clubs the pros are more than happy to sell equipment to non-members as well.

Is there a way to set up notifications for TT fittings? Or are you just regularly checking the website?

I’m not sure what Titleist uses for criteria - distance maybe? I’ve gotten emails from TT announcing locations to register for fitting times. In some cases duplicates from some of the courses that I’m on the mailing list. Part of that may be because I’m in a county of over 500,000 with over 20 public/municipal courses.
Checking the Fitting tab recently, I have seen Titleist fitters listed with no dates, but if you respond to it, they will add you to the mailing list for their next scheduled dates. If you list some of the larger metro areas to search for fittings, like Charleston, you might find more choices.
I don’t check for fittings for myself. I have a Premier fitter that I trust 3 miles from my house. I have relatives in WBGV and things I can take for granted are more arduous in rural areas.

We see Demo days at our local club. Not sure how widely (I expect not at all actually) they are advertised outside our club membership.

Maybe call around to your local clubs and see what if anything is coming up.

You can check in your area for fittings by going to the icon above "Fittings", type in your zip code and it will let you know fittings that are scheduled in your area at local courses. Give it a shot.

Be prepared to spend $100 if you don't buy anything though

You are going to be charged for a fitting anywhere you go. This stops the old days of going to a demo day, getting your numbers and taking to your friend, getting a discount by ordering thru them. Fitters deserved to be compensated and if you purchased thru them, it goes towards the purchase. Normally demo days are at clubs and are for members only. Sometimes you can find them a semi-private clubs and they will be listed on this site, plus certified fitters are listed on this site as mentioned in my previous post. www.titleist.com/fitting