Never priced them, but the rebuild kits are cheap and simple so buying a new one is a bit of a waste unless the housing on yours is cracked. Here's the guide I used to do it:
The heat choke connects to two lines that run into the block under a small panel in the intake on the passenger side of the carb. Those heat tubes feed into the choke on the passenger side of the carb.
You should be able to find replacement heat lines off any sbf in the local U-Pull-It; worse-case you could pull one to use as a template to bend your own.