I think this is what you are looking for.
which leads to here
and describes the syntax for the 'ip flow export layer2-switched vlan x' command.
I haven't tried it yet but plan to sometime in the next couple of weeks. I did confirm that the command is available from global config in that version of the IOS you are using so it should work. The next trick will be to identify what interface on the switch will be the source for the flows. I would guess the ones that show up as 'unrouted VLAN x - VLAN x'.
If you try this please post back your results and I will do the same if I get it in before you.