I bought one last week from http://www.Quantummodels.com. The price was pretty good, but not as good as http://www.CentralHobbies.com. Although the free shipping made the difference very small... I bought from Quantum because they had both the YS .63FZ and the Irvine .53 in stock and placing one order was worth the extra money to me.

FYI -- I put the new Irvine on my 2+ year old kit built SE. It is a drop in replacement for the .46FX that I had in there. I'll know tomorrow how well it runs...