This is a slight redesign from the one done by ggiavelli (Original creator Rocco81-92 https://www.thingiverse.com/thing:2858209/), I opened up the slot along the top.
There are three sockets on the PCB, so I have allowed access to all three so it probably works with other units which use the same PCB (I don't know what they are), I also opened up the sounder cover part so that it could be printed flat with no supports.
I later found out that the original author is Rocco81-92 and his was exactly what I was looking for in the first place, only for some reason it did not come up in the search results, and when I try to link to his design in the "this is a remix" option it does not come up for some reason? so use the link above to use his design if you prefer. UPDATE: I can now link to the original design by Rocco81-92.
I used ABS at 260 degrees C with a hot bed set to 110 degrees C.