Mochi Creams - SEA
You can get them at Uwajimaya or Maruta.
Baugette Box had them for a while, don't know if they still do.
Other Japanese restaurants may have them as well.
This is old hat in Seattle.
I've been having them since the late 90s...
(also make sure to let them melt a little bit before eating. they suck if they're super frozen)
I was curious if Mochi Creams are the same as Mochi Ice Cream, and from what I've seen, they are not. I think the other posters may be talking about run-of-the-mill Mochi Ice Cream, which is old hat here and can be found at a bunch of places.
If anyone knows where to get Mochi Creams, though, let me know!
Here is a description and some good photos of the Mochi Creams: