try your local medical supply house for a "holter" monitor & to get some brands /makers to contact, etc... or
So I guess this is what you are looking for ?
here is one
This crap is expensive... if you look around you can probably find something used..
Talk to a local dr... most have some free magazines that advertize 'for sale' used medical eqpt.
Some brands need a translator module to adapt to PC for download of data.
also you will need software for the analysis. If you buy a new unit it includes the SW.
This stuff is proprietary in general & uses nonstandard formats, etc.