what would be a good mat for a VPI SCOUT JWM9

I have a VPI HW 19Jr and I agree with Slipknot1, no mat. I clean the platter as needed with a very soft, lint free cloth and old fashioned, no additives, windex. It works very well.

I actually tried a mat because I had one from my other TT and agree with above it made the sound worse.

Sorry to have to disagree here, but both the Scout and ScoutMaster will benefit sonically in a very large way from the use of an aptly named product called the "Way Excellent Turntable Mat" from Herbies Audio (http://herbiesaudiolab.home.att.net/). This simple, inexpensive mat ($50) transforms the midrange to richer, warmer, closer to live music better than anything else on the market. It's so good that you will probably stop using the clamp unless the record is warped.

Wow. That's a lot to ask of a $50 mat. Anyone else experience this?

Nope. Tried felt, Sorbothane, Herbie's (btw, am a BIG proponent of the Grungebuster for CD's though). Mats on the Scout/Scoutmaster deaden the sound and muck up the pace and drive. Harry Weisfield designs this way for a reason. Give that platter a hearty rap with your knuckle (without a record on it, please). No ringing, no feedback.
Nuff said. But if anyone insists, I have a 95.00 Audioquest Sorbo mat I'll let go for a low low price....