I would like to know if anyone can recommend a very good top of the line scale and where I might purchase one. I have been looking everywhere but the choices are just too many and am looking for some first hand knowledge.

I am looking to weigh the portafilter. I am also looking for a scale that I can use to measure tamping force. I realize these are going to be two different scales but am looking for information on both.

Calibrating tamping force has to be one of the biggest wastes of time foisted on espressionists.
As long it's reasonably close each time, it's far more than close enough.
Even distribution, fairly accurate dose and level tamp reduce tamp force variation to insignificance.

This observation has been posted on HB before as well-

My wife and I spent this April in Rome. My routine each morning was to wander the back alleys and side streets following the locals to their favorite bars. After paying my euro to the cashier and standing in line at the bar waiting for my caffe, I'd watch every move of the barista as he pulled shots. Conservatively, I bet I visited 20 or 30 different bars that month (some more than once) and I don't recall ever seeing even one barista tamp a shot. The routine always seemed to be the same: charge the PF, then a tap or two on the counter to settle the grind, lock the PF in the group and pull the shot. Knock out the puck (some would wipe the basket with a bar towel, most not), then repeat.

FWIW-