How to preserve sort order in Excel Pivot-table?

Assign serial numbers to the data in another hidden column and use that to sort the pivot table data. If needed the serial numbers can be included in the pivot table and then hidden.

Serial numbers can be inserted either using a formula that adds one to the cell above or by typing 1 in the first cell and 2 below it and selecting both cells and then using the lower right hand selection point to drag the range down.