Meritline is offering this mini coffee lens mug for $4 with free shipping from China (arrives in 2-3 weeks). Please note this is NOT a regular size drinking cup. As you can see from the chain, this is more for decorative/novelty/entertainment purposes. According to the product description, it can hold 80ml of liquid which is under 3 ounces. A standard kitchen cup is 8oz and the smallest adult drink at Starbucks is 12 ounces. You can buy as many as you like at this price while this promotion lasts (I don't know when it expires). No coupon needed.
So we can call this a 80ml Coffee Lens Mug, where "ml" parallels the "mm" as a defining characteristic of real lenses :)