As a woman you have multiple tools at your disposal when it comes to revenge, but in my opinion, you're focus is on the wrong person.
Start with your husband!
Being a man, I know the best way to humiliate a man is through his ego. Now, this may no be your brand of revenge, but if I were a woman in your situation I would use the mirror tactic, basically do the exact same thing to him, but only with one of HIS co-workers, male or female, only don't go out of your way to hide it.
His co-workers most likely know whats been going on anyway. all you need to do is find the guy that hates your husband as much as you should.
Not trying to sound crude, but I think you deserve a little sport-fuck as revenge, and when he finds out, make a point to stress how good your lover was, and exaggerate his endowment, nothing make a guy feel more insecure than thinking your lady has been satisfied beyond belief by someone other than himself!