Nothing compares to the supple, smokey, salmony deliciousness of fresh, thick cut smoked lox but for a grab n' go snack, I love this Lascco Wild Caught Nova Salmon. I've tried literally every brand that comes through my local grocers, but this is my favorite.
At least here on the west coast, Ralphs and Whole Foods carry this brand. Should be $3.99ish for 3 oz., which is a PERFECT single portion at work or home - keep a cracked pepper shaker near your desk or use yours at home, and if you have a couple squeezes of lemon it'll be perfect (but it can do without it). It doesn't smell so your colleagues won't mind. It keeps for about a month, but eat it within two weeks. Guilt-free, delicious, and awesome.*
*If eating at work, keep a toothbrush and/or Listerine in your drawer:)