Keeping those sizes leaves very few options. The Cooper Cobras and The Mickey Thompson ST are the same tire (Cooper owns Mickey) 440 treadwear
Hankook and Nankang are also high treadwear ratings.
There are some Firestone Indy 500 available here & there, but the treadwear is 500 which is pretty hard and they're NOS so may be even harder.
I did run across these today.
American Racer tires from Boubin -::- - Products
Cheap prices. 295/50R15 @ $127 and the G60-15 (= the 245/60R15 is the width and dia) is $120.
I'm intrigued.