https://www.amazon.com/Globe-Scientific-1404-15-Cover-Thickness/dp/B00N50ZJBC/

I bought these after having issues with dirty cover slips off amazon. A lot of reviews for cover slips on amazon have the same complaint too, that they are all dirty, but these were mentioned by a user here named DietToms and they have been quite fine.

This is a case pack of 10 though, so its 10 cases with 148 cover slips in each, so 1480 cover slips (enough to last a few years).