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@György-Farkas Much appreciated... that does indeed start narrowing things down. Damn... why couldn't that be the real size... it would be a very easy to solder SMD part! As it is... doing a bit of digging, it seems like there are a bunch of them in different SMD form factors that suitable for USB (Torex XBP1002, Bourns CDSOT23-SRV05-4, Onsemi NUP4201MR6, Semtech RClamp0504F, etc) and would do the job... but they are either nearly $2 each, or minimum order 10, so looks like my Omega2 will just have to suck it up!
@Chris-Stratton My unsuspecting Omega2+ is going to be permanently connected to a 3D printer and running OctoPrint. so I have no intention of going to the hassle of sourcing a TVS just for that, especially since I won't be plugging and unplugging it. It would have been different if it had been said "oh, it's this 50 cent part here... which doesn't need a microscope to solder"