Beallara Patricia McCully Repotting Advice

[FourN6]

I recently received a very nice Beallara Patricia McCully still in bloom, although probably about to drop flowers soon. She's potted in a 4" flimsy square pot with bark, charcoal and perlite and the mix doesn't look awful. It appears some of the media went missing during shipping and the top half inch to inch is missing. The plant is extremely top heavy and falls over at the slightest breeze. Even supported in a ceramic pot she's still unstable. I'd prefer to wait until the blooms are done before repotting but I've never done a repot of such a tall plant. Can anyone suggest a way to keep her steady on her feet?