John King is (was) one fingerstyle uke player:
https://www.amazon.com/John-King-Cla.../dp/0634079794
Try `Ukulele Underground for lots of uke info:
http://forum.ukuleleunderground.com
Mark Nelson has several books on fstyle uke:
http://mark-o.com/buy/books/
Led doesn't have any material out but his playing is inspirational/daunting:
https://www.youtube.com/watch?v=ohPC5aYN6zI
https://www.youtube.com/watch?v=PPkrJzKsNyk
Herb Ohta Jr. follows in his dad's footsteps and does wonderful things on his uke. Here he teaches an arrangement of "Sanoe"
https://www.youtube.com/watch?v=mEfkazmxcBM
Fran