You can find Dulops around but the 240 D407 Dunlop is an OEM tire and I imagine that's why your indy shop is pushing you to Metzler.. Better price point for them.. Dennis Kirk also has the Pirelli Diablos 240/40 for $163.. I got nothin on how long they'll last though..
Check the search part of the site. I've read posts about guys getting 10k miles out of the Metzler ME880 series, but I've also heard of people getting closer to 4k out of them. They're supposed to handle better than stock Dunlops in corners, and especially in wet conditions.
i got rid of the dunlops and use metzlers. they are pricier than dunlops and they don't do as many miles as the dunlops BUT they are better performance ..... basically if you want better performance and can afford the extra bucks then metzlers over dunlops any day. Having said that my local dealer is trying to convince me to go to a dual compound dunlop on the front.