turn the speakers on quietly, or just download podcasts to an mp3 player. seriously dude, using the words cheap, wireless, and earphones in conjunction is like asking for something that either won't work right or will break before long. there's just not a market for it; most people who really want wireless headphones are willing to pay extra for it, so it's not likely to be found in something cheap.
but hey, if you can find something, awesome. i think your best bet is to try to find a used set of wireless full sized headphones (as i believe these to be more common than wireless earphones).