Mystery lithops

I got this guy back in the spring, from a nursery, sadly unlabeled. I know that nursery lithops aren't supposed to be that great and often die unexpectedly. Much to my surprise this one was happy enough to flower! And a pretty white flower at that.

Still stumped about the species though I'm hoping the flower colour will narrow things down. Maybe a L. karasmontana?

Anyone have a suggestion?