Good question. I have 30-40 players I track because I believe they are eligible for the Australian set-up, many of which are under the age of 20. Coincidentally I am cross-checking that list with Football Australia for accuracy. Some of the names that are playing at a reasonable senior level that may or may not be known to those on this forum:
Melos Bajrami (24, defender, currently in Albania top tier)
Tomislav Glavan (21, forward, currently in Austrian second tier)
Charlie Cummins (20, midfielder, currently at Exeter City)
Ayom Majok (22, forward, currently in Malta top tier)
Obviously guys like Ayman Gulasi, Markus Walker and Cillian Tollett are frequently mentioned here.