He has stated that he and his mother went to a fabric store and got some fabric they thought world work and his mom made the costume and that he is aware it isn't the ultimate figure skating costume or some such. Personally I prefer it to the Vera Wang that was always riding up on him. I doubt he plans to keep it all season.
The costume hippomoomin and bonita were talking about is the one he currently uses in his SP, which is basically an off-the-rack shirt and vest, hence the bad fit and stiff fabric, which are eating up his neck.
The one that his mom made is the top of his FS costume, which, save for some creasing, doesn't bunch up on his neck, so not as problematic. Although it's a shame that it covers up the shape of his upper body/stomach area because of how loose it is in that area. And the way it hangs down during his camel spin, really ruins the overall shape of the camel, but other than that, the loose fit actually fits his casual and unconstrained skating style.
I'm surprised that you feel his Vera Wang costume was always riding up on him, since her designs for him have all been form-fitting like a full body condom err wet suit

unless you're referring to his last season's FS costume? That one was just an emergency solution I believe, I don't think it was ever intended to be his actual costume, but more like a kind of sweatshirt for warm-up, so the fabric wasn't elastic or flowy enough and would indeed ride up whenever he raised his arms.
Speaking of costumes that are too loose, reading the current discussion about Jason's SL made me rewatch that program, and I still can't get over the strange fit of his pants, especially in the knee area.

The way the excess fabric stretches in the back of his knees makes his legs look like tent poles and the pants, accordingly, like a tarpaulin. It creates some really odd looking lines and shapes whenever he stretches his legs, particularly during his spiral or camel spin.
ETA:
I think that the story about the Nathan's costume makes it much more charming
I read people in the comments on Jackie's twitter saying that now they can't complain about the costume anymore, for momma Chen's sake, so cute!.
ETA 2:
The tour bus inspired free skate costume
I love how this has become like an official title for it now.
