I'm a bit unclear... Do you want a double battery case that will carry one of each? I don't know that I've seen one, you could get a battery case for your larger size battery, and then pad the other side with paper towels to make it fit, so that it won't be rolling around in there. I guess your other option would be a single battery case for each, that way you wouldn't have to worry. I think many of the major battery sellers include cases, but I have not purchased any of the 27- series
batteries, so I'm not really sure about where you could get cases. I guess you could try
fasttech, or one of the larger USA vendors may sell them. If you order from FT now it may be a slightly longer wait due to Chinese New Year.
Best of luck, and I hope you find what you need.
Anna