Throttle cable.

I have a 2000 Toyota Tundra. Today the plastic throttle body return spring unit that holds the throttle cable broke and will no longer hold the cable in place. Do I have to buy an entire throttle body from the dealer, or find one in a junk yard and scavenge the piece I need?

 

Somewhat hard to tell from pic but from your description and somewhat via picture, that appears to be the TPS(throttle position sensor). If so, junk yard is a good choice or even MacGyver and bailing wire.

As for a new one, without more of your trucks specs, this is a simple search at McGeorge Toyota for a new part which isn't too bad a price....$80

1998-2002 Toyota Throttle Position Sensor 89452-30140 | Toyota Parts (mcgeorgetoyota.com)