If it's not the filter then its the front main. If its around the front bottom of the engine you might want to tighten the oil pan just to rule that one out. I thought mine was coming from the oil pan gasket, but when I did my timing belt I changed the front main and it went away. It's a big job so the $25 UV kit sounds like a good investment, just to be sure.

Or just clean the engine really well and let it idle, don't drive it, since the wind will blow the oil away from the source. That should give you a better idea of where the leak is coming from.

1989 Montero LS (sold)
1994 Cherokee Country bone stock