Newegg offers the Kingston DataTraveler 32GB 100 G3 USB 3.0 Flash Drive, model no. DT100G3/32GB, for $6.99 plus 99 cents for shipping. That's the lowest total price we could find by $3, outside of the mention below, and the best per unit price we've seen. (We saw three of them for $30 in May.) It features a sliding-cap design.

A close price: Amazon has it for $9.22 with free shipping for Prime members.