We might have this option in the future. But it requires some additional work to set up.
However, if you email registration@kumoricon.org, there is the possibility they can accommodate this sooner (I don't think so, but I don't know the answer for certain). Keep in mind you can also mail in your registration by check or money order, and if you are wanting to register by Dec. 31 (before the price goes up), as long as it's postmarked by that date (not necessarily received), then it's valid for the current price.