Unfortunately, you're right - I went to addictedtorc's site and saw the cups when I clicked on products for E-Savage. I assumed they were for the E-Savage, but now I see they're not direct replacements.
If the MT-2 pieces fit, then these guys sell a alum diff cup -
http://www.novarcproducts.com/diffcups.html
Sounds like if you're sticking with BL, you don't have many choices to solve your diff probs.