from PySide2 import QtPrintSupport, QtGui, QtWidgets

class Window(QtWidgets.QMainWindow):

    def __init__(self):
        super(Window, self).__init__()

        self.combo = QtWidgets.QComboBox(self)

        self.setCentralWidget(self.combo)

        printer = QtPrintSupport.QPrinterInfo.availablePrinters()[0]
        print(printer.printerName())

        self.combo.addItem(printer.printerName(), QtPrintSupport.QPrinter(printer))

        # Fails
        assert(isinstance(self.combo.itemData(0), QtPrintSupport.QPrinter))

app = QtWidgets.QApplication([])
w = Window()
w.show()
app.exec_()