Hi Tim! I don't use Craigslist directly. I use a site called Search Tempest. In the "What" section (top left), I put "core sound" in quotations. I think choose boats for category, and put in any distance. You can then open the tabs for all 8 sections of the continental US.
You can also search Facebook Marketplace on there, though there are a few more steps.
When I was searching for various boats a few years ago I had running searches I would do each day (eg, "Core Sound", "Welsford", "Vivier" "Norseboat"). It helped me find my boat in CO at a very good deal!
I think currently Facebook Marketplace has more boats than Craigslist. A fun daydream activity is to use the search term "wooden boat", set the price over $250 to filter out the stupid model boat decor, and then move the search area to new england, florida, and PNW to see all the really cool boats there.
Also, Sailing Texas is a great site. I haven't seen many Core Sounds there recently, but you can check their Sold page to see what's been on there.