I like the mat we have as it is as wide and long as the machine, so it covers the entire area where leaks could occur. Some patients here use Watch Dog type alarms which are very small in size. They buy several and place them in strategic spots where a leak might occur. But they have wires hanging out and can easily lose their positioning. I am much more comfortable with the mat I have as I know it covers the entire area. You said something about yours fitting in a bucket. That would work for the dialyzer, but what about dialystate or saline leaks?
Also, I read a post where a caregiver said that one time the dialyzer started spraying blood due to a loose cap. In a case like that which sounds like quite a mess, I am wondering how one could in some way cover the dialyzer so blood woudn’t get on everything. For one thing, it’s a good idea to always check the cap before starting tx. And of course it would be a rare happening. But I’d like to know I was prepared if something like that ever occured.