These were included in the Heller and Italeri issues of the venerable AMT kit, however not in the original. They can bee seen to the right in this sprue shot
If anyone, by chance, has built any of these kits as a KC-135R without these pods, I would be most interested to buy them. Also, any pointers towards aftermarket pods like these would be most appreciated. I am aware of the AIM Cobham 907E pods for the A310 MRTT, but I don't know if they are similar enough.