This might do nothing, but I’ll suggest trying it anyway (I can’t do this myself because I have everything in the bundle).
For those who have the party bus, and not Lady Duff, have you tried storing the party bus?
I remember a while back a similar fix for a bundle (it was Freedom and Bush’s House - if you had Freedom, and stored him, the bundle appeared. It didn’t work the other way around tho).
It’s a long shot, but worth trying.