all i know of is fluteworld, and their piccolo selection is lacking(4 used piccolos...)

im looking for an upgrade from my old yamaha(1970's ypc-61)

You might take a look on usedflutes.com. I would make sure you get a trial period, and send it directly to your repair tech so he/she can estimate the cost to put it in perfect working order.

Nancy Shinn of Flutestar might have something for you.

I saw a Zentner on Liz's winds101 website the other day.

Ebay would be more risky, but if you can find one with a good seller, a trial period and send it directly to your repair tech, you might find something really nice.

Carolyn Nussbaum currently has three used grenadilla piccolos for sale on her site:

http://www.flute4u.com/store/cart.php?target=category&category_id=260

http://www.yourfluteworks.com/piccolos.html