Check online. Odds are you can find one of the newer TV tuners with the CX2xxxx chips as opposed to the older BT8x8 chips, and for under $75. ASUS makes one, as I recall. The CX2xxxx chips have 10-bit ADCs, so the color is a bit better than it is on the BT848/878-based tuners.
Make sure whichever one you get has stereo.