Today only, GNC offers a selection of supplements for $5 as part of its $5 Supplement Sale. (Discount is applied in-cart. Click through the "$5 Sale" banner on the side) Plus, all items ship for a flat rate of $2.99. Some best bets:
Note: This item is part of Amazon's "Add-on program;" it can only be purchased with an order of $25 or more.
Of note, be sure to cancel Subscribe & Save after your order arrives to avoid being billed for subsequent shipments.