How old of a hard drive?
My old hard drive is barely 3 inches total!..............
Ah, it s gotta be the old larger ones, can’t remember the size now, but over 5 inches I beleive, the old PC hdds. Not laptop ones, though those might have them too, but smaller. If you have a computer repair shop nearby, you could prolly get some real cheap, ask for junk ones. I got a few that way. But also have 4 or so left over fro pre sdd days
The link shows the size, though they do show smaller ones next to it in first photo too, so they likely have magnets too
Too Much Information.™ :-D