You may want to contact the State's Parts Locator Hotline. We've also been unable to find an exhaust manifold for your 1984 Chevy Blazer with the heat shield and stove pipe attached. You might be able to find and install a heat shield with stove pipe attachment as a separate unit. Check with the parts locator.
The State's Part Locator helps motorists locate hard-to-find emissions parts that are needed to bring their vehicles into compliance with state law. If the parts are not available, the they may be able to issue you a "Limited Parts Exemption". In most cases the needed parts are found. You may contact the State Smog Check Parts locator by calling 800–622–7733.