Get an MK 15 series rebreather
Seriously, there is no way that I would modify an Inspiration to dive to 200 meters. Even when fixing the buzzer and any other mechanical aspect of the unit, the scrubber itself is simply too small: even if you were to limit your bottom time to 5 minutes - you have to ask whether the dive is worth it if you stay so short - you are still talking about roughly 18 minutes below 100 meters plus the time of any deep stops below 100 meters (3 minutes to desent from 100 to 200, 5 minutes at the bottom and 10 minutes to ascent to 100 again), and there is no telling in advance how the scrubber will behave during that time and at such depts.
Rgs,
Niels Doorduijn