Older Triton TR60 parts

Hi all, It's finally stopped raining here in Wisconsin. Well, at least for today. I opened my pool this week and have a problem with the drain valve on my sand filter. It's a very old Triton model TR60. Last year the petcock was leaking fairly significantly, about a drop per second towards the end of the year. So this year before filling the filter, I took the petcock off and put new O-rings in the handle shaft. It's still leaking. Before I take it apart again, I'm wondering if I could just remove the petcock and replace it with a plug. If so, is it a common size that I could get at my local Ace hardware?
Thanks