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Hyper Purple Lvl3 is obtainable from the Power Plant Robbery, in order to get a lvl3 one, you need to have a lvl2 hyperchrome in your inventory.
Recently, a lot more people are interested in trading for Purple LVL3 (most likely to grind it to LVL4/5). Its often looked for by traders now, and can even get Aperture quite consistently (despite Aperture being of higher demand). It can also get similar overpays in mid demands as Red LVL3, which is currently also at above average demand.
Supply is widely distributed — no single holder owns enough to register as a hoarder.