Amazon offers Prime members the RCA Indoor FM and HDTV Antenna, model no. ANT111F, for $3.99 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $6.19.) That's $3 under what you'd pay at a local retail store. It features a no-scuff bottom pad and can be easily repurposed as step one of a decent robot costume.

Note that this item is currently out of stock, but can be ordered at this price with an estimated in-stock date of May 6.