Home Depot offers the Anchor Hocking 4-Piece Palladian Window Set, model no. 97564A, for $17.50. Opt for in-store pickup to avoid the $6.49 shipping fee. That's tied with our mention from a week ago and, outside of the mention below, the lowest price we could find by now by $4. This stainless steel set features an air-tight seal, viewing window, and multiple sizes.
A close price: Walmart has it for $18.99 with in-store pickup.