Are these a Subaru replacement part? If not anyone know the size? I have maybe 3 that need replacing..

Take one to Ace Hardware you should be able to match the thread pitch.

 

Or 

 

Hit your local yard.  Easy to pull a few.

take one with you. 

10mm head & M6x1.00 I believe

Aftermarket suppliers of fasteners would have such screws in bulk quantities, with captive washers like the originals. I got a bag of 25 (if memory serves) just in case, after noticing the washers were rusted on the transmission pan screws (same part) while replacing the gasket. The screws are also available from a dealer at a reasonable cost.

Good I will check into it.

Screws are good, now what about that o-ring on the oil pick-up tube? I can't seem to find a part number?