Asked this question in another part of the forum but got no replies. Thinking of modifying my offset smoker masonry side firebox to install a cast iron access door in the sidewall. Seen some used in various pix of builds by others but no information was included as to where they were obtained or their size. Best I'm able to find is a fireplace 8" x 2" clean out door. Not what I have seen used by others. Anyone have any suggestions on what to use and where they can be purchased?