The Robin Casady plate for the Mewlon 250/TOA150 would be the best out there. Robin has retired but there were still some of the large Tak plate left. Not cheap though but the quality is exceptional. I have the Casady saddle and EM plates, they are the best I have seen.
Lookie here:
http://www.robincasady.com/Astro/LgTakPlate.html