Yes, but I'm at a current low for the past few decades of about 8-10 of them.
I had an EX250 on the street for a bit before I turned it into an AFM 250 Superbike racer (the original plan was to build a custom framed one for the F3 (125 GP) class.
Euro Spares - The EX250 + 125GP = ? article
If you think it would be of any use to you I've got a Specialist II race exhaust system for a Vision (I think you've mentioned having one of those) that was on a friend's racer for 4 or 5 races in the 1990s. It isn't doing me any good sitting in storage and it is yours if you think you want to mess with it.
Any aftermarket exhaust for an EX250 I've seen has generally been 2 into 1s with large headpipes and minimal silencing, so I'd recommend you stick with the stock exhaust to start.
I've always been a racer and fuel economy hasn't been a significant concern (I deal with economy by driving on the street as little as possible) but I am interested in extracting power efficiently and not throwing it away with bad aerodynamics. I've got an FF project among all the vintage dirt bike/roadracers/piles of "there's a bike in there somewhere" stuff.
cheers,
Michael