I have never owned a 192, but have owned several 182s. Make a pattern from cardboard. Buy some 1000 denier cordura and buy some 1" fire resistant closed cell foam to fit in it. Then sew it together. Buy double of the raw materials in case you screw up. If you get it right first time, yer set up with a spare in the case you wude remove one to wash it. Yer profile says yer a senior rigger so you shude have enuff skill to do this. If you do not have enuff skill, this cude be good practice for you and its possible it wude help with yer future sewing projects. Put a couple of velcro or bungee tie down loops on the down facing side so that it wude not follow the jumpers out of the plans. PS When you see how ridiculous this response looks (even thought it is valid), it shude give you an idea as to how serious people take yer comments.