Would it be possible for the clip to changed a bit?

I rather like the rectangular style of clip from the Regular Bulkfiller, as opposed to the rounded one on the Kingsize. It that possible to do?

The Kingsize clip only comes in one shape.

In the early years, both a rectangular as well as a rounded one that was also tapered existed.
For manufacturing purposes as well as aesthetic reconsidering, we merged both designs to end up with a straight “parallel” clip with rounded ends. So this is the only choice sadly.