OK sorry if this has been done before.
I noticed that those little plastic boxes that business cards come in are also perfect for fitting in a couple of Mr Kiplings type slices when you're out for a ride. When you stop, Hey Presto! No pulverised cake.
Kinda works like those banana cases.
Other brands of slices/tray bakes may also fit or, if you're making your own, simply cut to size.
