There was another cassette type frame posted a while ago:
http://forum.honeyflow.com/t/interesting-way-to-get-bees-to-make-pre-packaged-honeycomb-honey/9730?u=faroe
Don’t know if anyone tried it yet.
The other option is getting a Flow Super Hybrid and popping that on top of your super and you will have half honeycomb, and half Flow Frames.