My brother needs a rim to replace an OEM 15" rim on a '98 OBS. We haven't found a local yard that has any Subaru rims.

What other makes/models would have a compatible 15" rim that we could ask for? It doesn't matter what it looks like, just that it can be used with the 3 already on the car and the tire we have available. Is weight a concern in terms of maintaining symmetry?

your wheels need to be symetrical due to the awd.
Where are you located?

The car is in Northern Illinois (around the 61008 zip code).

After sliding off the road in the snow, he was having issues with front-end noise and/or alignment. He took the wheels in to check the balance, and they told him that one of the wheels was bent and couldn't be balanced.

Since there was no impact when he went off road I am failing to see how the wheel could have been bent, but this is what the tire shop told him.