Thanks for all the responses! Neither Boardsports, nor Spray Lake wanted to do it, but the shop at McClintock's said they would replace the fin for just 20$. It's not far from where I work, so I will head down there tomorrow.
The ski felt a bit funny the last couple times I skied, which is why I started looking into this. I am not sure if it's also possible that the fin moved a bit. Unfortunately I never took the measurements on the fin, so I can't even tell.