I thought that may be the case MM ,if the saw had a shallow round recess ,I guess you could easily block the hole with a cork or round dowel ,even if you had to make one by putting a small bit of wood in a drill chuck and spinning it against a pedestal grinding wheel.Probably quite a few other ways to block the oil leak too.
I would just drill a hole in the oil cap after the oil leak is blocked and use a valve stem from a motor bike tube as it has a longer thread then just use 2 lock nuts ,one on each side of the oil cap ,on the outside of the cap you wouldn't need much of the valve stem sticking out ,also I would drill a hole in a valve cap end and put a tiny sponge inside the valve cap and that will stop any dirt getting stuck in the valve..
Up to you though if you could be bothered ,I just know if it was me stopping all the time while cutting and using an oil can would drive me crazy .
