Well, it is a Dimensions kit and if you have been following the posts on this chat at all you will have learned that they seem to have a very poor record of supplying extra floss, if at all.
If it were me, I would convert the Dimensions colors to DMC. Using DMC you won't have to worry about ever running out.
Do not follow Miss C's advice. It makes no sense to begin a large project not knowing if you will have enough materials to complete and all the while hoping for the best.
It's a very cute pattern. Good luck.
PS Yes, you would have to contact Dimensions directly either via phone or email. The info should be listed on the pattern.