Hi stemked,
I don't have the lens, but what you need in a plate is one that is long enough so you can balance your camera/lens combo on the head, and one with at least one slot so you can use both attachment points. There are countless sources for A/S compatible plates at this time as the mounting system is adopted by more head mfgs, so you can pretty much choose your source once you determine the length you need. My goto sources for A/S plates have been Hejnar and Sunwayfoto as they both offer pretty full lines of plates and clamps, but I've had just about everything I need for my support system for quite a few years, so I may not be aware of other good suppliers that have appeared in the meantime.
Hejnar Photo - Design Manufacture Delivered http://www.sunwayfoto.com/e_index.aspx
Hejnar will also make custom plates to the user's specs.
I'm sure you can find bargain priced plates from a number of sources, but you just paid a premium for a pro level super tele zoom and I assume you also have a top end body. IMO it deserves a top quality plate, but YMMV. . .
Scott