Nordy posted this on the PG site a while back. I purchased one for my PG 500. Not as heavy as I would like but it serves the purpose well. The link was on Amazon, but didn't come through, but go back and look at the link
"Posted March 15, 2012 10:16 AM Hide Post
Though I can't comment on the PG500 but this is the one I use on my PG1000. I use the 70" XL size, perhaps one of the smaller sizes will work on the PG500. "
Pellet Grill Cover