TR58 can be found as a reward for doing max raid battles in Bridge Field, Dusty Bowl, Giants Mirror, Stony Wilderness(Sh), and West Lake Axewell(Sh).
It can also be purchased from the Watt Traders for 3000 watts.
Finally, it can also be obtained from the Cram-O-Matic by inserting a Dark attributes item and 102-110 points worth of items.
Hope I Helped.
