Since the bottles themselves aren't always marked, you could grab this set of bottles with droppers and combine it with this set of polycone caps just so everything's clearly specified. I think they all use the same thread measurement (the 400), but the 20/22 neck diameter seems to be pretty arbitrary lol.

Edit: Also if you like FA Forest Fruit (which I absolutely do), I've found this recipe really hits the spot for me. You definitely want to halve the sweetener to start, though. TFA Greek Yogurt isn't exactly a utility flavoring, but Billberry is nice to have a round and wouldn't be a bad pickup on a future order.

Edit: Fixed link.