Simon suggested the Pride of Petravore (also known as Eileen Og) and although it is often played with Rights of Man, it would also go very nicely with Four-Up.
There are many versions on thesession.org, so we’ve picked the most straightforward one, but feel free to add more notes if you want to.
Petravore is often played on YouTube, here are just a few of the slower versions I could find:
Nice and slow by a group in Germany
Tin whistle but no video
The Craic Addicts
On a banjo
Another Tin whistle
Nice and slow wooden flute