Black plastic plugs for me as well, got them at an auto parts store in the upholstery trim section. Also put them in the holes where the brass plugs got drilled out to adjust the jet screws.
WARNING: This is one of the Mod Monkey's favorite places to spend your money at, with all the goodies on here the checkout price can be epic! You have been warned! This warning brought to you by the VMFAMMC (Vmax Forum Anti Mod Monkey Coalition).