A box of biscuits
A box of mixed biscuits
And a biscuit mixer.


My mother's version had it
..Six boxes of biscuits
..six boxes of mixed biscuits
..and one biscuit mixer.
and as often as not it came out "bisket misker"

She also had just plain "rubber buggy bumper." I tried to expand that, wound up with a "really rugged rigid rubber baby buggy bumper" but decided that the rhythm actually made it easier to say correctly

And of course there is the classic "She sells sea shells by the sea shore."