Can not purchase Holiday chromas

I got Winter Wonder Soraka in a hextech chest and I would love to purchase the chromas but they are unavailable. I understand the skin itself being limited but allowing the purchase of the chromas does not undermine the intent of limited skins. I think since this is only the 2nd batch of holiday skins, this is just an oversight and riot has not made a policy regarding holiday skin chromas. I made this to open up that discussion.