Google GPS tracking and you'll find a plethora of relatively cheap solutions.
As you say not Alzheimer I'm assuming he's aware of what happened and wants that tracking too.
If not, it's going to be harder as there's likely legality problems as well as the possibility of him dumping the tracker to consider.
Reductionist and proud of it.
Being ignorant is not so much a shame, as being unwilling to learn. Benjamin Franklin
Chase after the truth like all hell and you'll free yourself, even though you never touch its coat tails. Clarence Darrow
A person who won't read has no advantage over one who can't read. Mark Twain