First of all, the fact that you are concerned about being fair to your agent is HUGE!
We need more clients like you!
Unless you have a rep agreement in place for your lease search , you are most likely not obligated to pay anything.
If I was the agent , it would be nice to get a hand written thank you card, a gas card to refill my tank ....and maybe even a referral or two down the road!
You would not believe the lack of gratitude agents receive ....your a good person and a dying breed.
All my best.