Welcome to the board.
To my knowledge the parking brake lever isn't reproduced, however there are lots of people doing rear disk conversions around here that may have that part laying around with no plans to use it in the future that may be willing to sell it cheaply or give it away if you pay the shipping costs through paypal.
If you don't get a response here jump over to the classifieds section and take a look around and maybe respond to a few advertisements asking if they have that part available.
http://67-72chevytrucks.com/vboard/forumdisplay.php?f=8
Remember as a non-paying member you can only buy parts you can't sell or post new want to buy (WTB) advertisements.