if your push/pull/leg routine is set-up properly, all you need is extremity/accessory work to that end. I wouldn't do bis/tris as this would interfere with the push/pull. I think Stu's suggestion is good.
I'd probably go at lunch, and do variations on abs, single joint dumbell lateral side raises (push pull always tends to ignore this aspect of the delt), calves and stretching/foam rolling.
That way I wouldn't need to shower before getting back to work, like I would have if I did cardio.