Sadly it doesn’t look like she’s selling them but on the other hand I don’t think that it would be that difficult to make one yourself not that you have been given the idea. Heck I can’t sew to save my life and I reckon I could make one.
Sillysparrowness is apparently a German teacher and a YouTube Sensation (If she wasn’t before she will be having built a TARDIS, that’s how the internet works isn’t it?) In the above video she goes through the trials and tribulations of building a collapsible TARDIS.
The video is worth watching if only for the “Bag of Shame”.