Corporate pilot reported a wing fuel leak during cruise. The flight crew diverted and after landing Maintenance found two missing wing rivets.

Narrative

I was on an IFR flight plan from ZZZ to ZZZ1. Center had leveled me off at FL240;I was waiting for further climb clearance as I had filed for FL280. It was at the moment VMC; but out of habit I checked the wing for ice. That's when I noticed fuel leaking from the wing. At first I thought it might have been the fuel cap; but it was secure; and then I realized the fuel was coming from under the wing. I turned to get the attention of the owner of the aircraft; who is also a qualified pilot; that had extensive knowledge of the local area we were flying over. I waited until he got in the right seat and buckled in before taking any further action. We then [requested priority] and started an emergency decent. The owner was helping with radio calls; and headings; we coordinated with center; and decided to land at ZZZ2 as they had 8;000ft of runway and fire services on the field. Center passed us off to approach; and Name was on the second com coordinating with tower. Approach then passed us off to Tower; who cleared us for a landing on Runway XX; but since the winds were not a factor; 110@3kts; we requested Runway XY as it was the closet runway. Tower quickly gave us landing clearance for Runway XY; and I entered a left downwind. From that point on it was normal pattern; and with all checklist complete; a successful landing was executed. We then taxied off the runway to Company where we greeted at shutdown by the fire dept. to inspect the wing. After further inspection we found the wing was missing 2 rivets; and we calculated we were losing approximately 1 gallon of fuel per minute. No other damage was noted in the post-flight inspection.