Considering how difficult it is to even obtain this figurine.. Your best bet is to make your own stand. Some plastic epoxy should be more than enough to glue a plastic rod to a plastic base. As for the weird shape where it connects to and holds up her hair.. You could use a small block of modeling clay and press it into shape on her hair to get the 'form.' Shape that clay into a rectangle and just stick it on top of the plastic rod after baking it to harden. The weird shape might be hard to 3D print unless you have some way of scanning the geometry or know a fair bit about CAD software.
Could also try bending a wire clothes hanger into shape. Shouldn't be too hard with a couple pairs of decent pliers.
Best of luck. Shouldn't take too much DIY.
https://www.amazon.com/Clear-Miniature-Bases-Circular-Inch/dp/B00MV52W80
Alternatively.. Should've said this first but I didn't think it'd be so easy to find. You could try a doll stand. I measured my figurine and the plastic stand is about 6.5 inches from base to top. I *think* this stand would work. I think it can adjust up to 7 inches max height which would be perfect for the 6.5 inch height on the original stand. After getting the proper height on the stand I'd probably put a glob of hot glue inside the adjustment part so that it can't slide down with gravity.
May your Holo live on.