If your trying to stick with a trusted quality brand name EBC and Stoptech both make slotted only rotors, they aren't too expensive.
Otherwise there are a dozen various brands on ebay that make all kinds of colors and combinations of slotted, drilled, dimpled rotors for dirt cheap. It can be hit or miss on how long the coating/finish holds up to the elements or hold well they wear. You'll have to use your own judgement there.
I have Powerslot Cryo slotted rotors and love them
Powerslot rotors are Stoptech it's the same company, and both are just subsidiaries under Centric..
Both can ordered Cryo treated or not, just add CSL (left) and CSR (right) as the last three digits on the part number for which ever style of rotor from either division and you will get the cryo treated version.