Finished my bell jar shatter guard tonight. Made it from a piece of perforated steel from a 24" rack cabinet door. Top was some sheet metal at my dads shop. Cut it into a circle with a Beverly shear. A piece of 1x1/8 steel strap was rolled to fit the OD of the top. Then tacked them together. Today I broke the clamping edges and mig spot welded the perforated steel to the top and made a hook for the jar lift to grab on to. Hit it with some black paint and called it done. It clamps on to the jaw with some very soft rubber around the bottom edge.
Finished belljar shatter guard by macona, on Flickr
New shatter guard by macona, on Flickr