Whenever I can't find something I filter on the EP or SP it came from, or filter on the store. That greatly increases the chances of finding it.
Another thing I did was to use a 30x30 lot to build a Supernatural Park which had a garden and I built a toilet block. And added a picnic table, a fairy house, the fountain of youth (from Hidden Springs world), the Arboretum, Gypsy Caravan and Vault of Antiquity to the lot.
https://i.postimg.cc/gJg8mnQb/Supernatural-Park8.jpg
I place it into any world and I've got all the supernatural rabbit holes together. It is in my studio and was built long before I started adding mods or custom content to my game.
If you do have the Fountain of Youth you will need to replace it when you first place this lot. I've got that fountain on several lots I've built over the years and I find it never works when I first place the lot. So the routine is to place the lot into a world and then edit it to replace the Fountain of Youth.
This is the link to my build just in case you might be interested.
https://www.thesims3.com/assetDetail.html?assetId=7940407
Happy Simming
