Anything along the lines of Hanssen's, Tilquin, Girardin are going to be easier to find and with about 95% of the deliciousness of the tougher stuff. Drie Fonteinen is my hands down favorite "shelf" lambic. Will just mention Cantillon of course but the more lambic I drink, the more I find the classic Gueuze to be a bit one dimensional (but still stellar). Hell I wouldnt even turn down Lindeman's.
The harder to find stuff (A&T, Armand Seasons, etc) are by far some of the best beers I've ever had, but diminishing returns for the pain in the ass of obtaining them.
If you're ever town and want me to open up a couple - I'm down.