Grant,
The Pioneer OS450's that Billy mentioned are the ones I was thinking of. The brand really does not matter, any Small Block umbrella from the late 70's should be the same. Your machine shop should have them, I keep a box of 100 on the shelf
Another option is to just put a small block "O" ring on the stem below the retainer. I had a customer years ago that used them on his BB engines and claimed they worked pretty decent. I guess anything to keep the oil from running down the stem would help.