I recently built a Division 6 Business Card Sequencer and decided it needed a case. Division 6 sells a case, but it’s almost as expensive as the kit itself.
It turns out the sequencer fits in a cassette tape case. I had to gut it, clip some of the internal molding, and cut the top of the case to allow access to the buttons. I used a fine-tooth model saw to get the vertical cuts in the case top started, then scrored the plastic with an exacto knife on both sides to set up some stress in the plastic so side wire cutters could snip the rest away without undesireable cracking or splitting. The original styrene clear tape case had an opening ‘cut’ by means of an old soldering iron tip – it’s very hard to cut styrene otherwise without it cracking.