Have you seen Frank Reese's? He has White sports from Golda Miller's black line and he has had them for 50 yeas. Here is a picture form his facebook page.
I was JUST speaking with a Black Giant breeder friend yesterday about Whites - he's got some coming from G. Donnelly - supposed to very nice.
There are not a lot of good whites out there; there are a couple of folks on BYC breeding them, but the lines are not very good in my humble opinion. I do have a breeder friend in Oregon who had put together a group of folks to breed the whites...that was last year, not sure how they're doing now.
I think, from a general viewpoint, the whites need lots of work. I'm glad to see there are a few folks comitted to working on them!