I checked into this and that option is in the Bars command but not in the Pivot command. We will look at adding in the future to the menu at the bottom of the Pivot where you can format the error bars.
For now, you can overlay two Pivot commands, one that has the mean and SEM and the other that has the mean only.
To do this quickly, select a command, use command-C to copy, command-V to paste. Have the second command in the list set to mean, It will overlay the first and create the look of the error bars only going up.
I also added this file to the example files (Files > On-line examples), though it has bars in both directions.
Does this help?