I saw stuff like the ones on e-bay at the Kreitz racing flea market last Saturday for as little as $10 each. I haven't seen any ads yet, but I hear there may be another flea market at Mahoning this weekend. Maybe you could find what you want there. K&K (609-882-8927) had a lot of used asphalt slicks for sale there.
K&K also has new 6" Majors (soft compounds) for sale. We ran them at Snydersville many years ago very successfully. More recently, in order to comply with the track's Burris rule we ran the treaded Burris tires all season without wearing them out. Personally, I would prefer NEW tires to start the season. A full set can still be purchased for under $200.