Hi Brianna, welcome to the forums!
Your post has been moved here, since it is a question that comes up quite frequently. Also, the information in this thread may help.
So, my question is ... which publishers still use the classic Hyslop font? Egmont is obviously out of the question. I think Mammoth does ... what about Little Brown Books?
As general rule, anything published before 2004/2005 should have the Hyslop lettering*. However, the dates can make things complicated since the copyright information given at the front of the newly-lettered Egmont editions doesn't mention that it was a new printing. I think some of them say 2002, which is wrong...
Therefore, it's easier to go by publisher. Anything published by Mammoth or Methuen (or Magnet in paperback) will have the original lettering. Egmont did publish the books with the old lettering, but as I've mentioned, the dates have gone awry and make it hard to identify which copies have it. I don't know about Little, Brown books, as I personally haven't seen any copies to verify when, or if, they've changed the lettering. Somebody else may be able to shed light on that.
I hope that helps!
* note I say lettering! It isn't a font, although many people call it that. It was hand lettered by a cartographer called Neil Hyslop employed by Methuen Children's Books back when they were publishing the books. I know that English language is evolving all the time, but 'font' used to mean complete set of type of one size and face, although people use it now to mean 'typeface' - at some point in the future it probably will
come to mean any form of lettering...