Thanks to @Jean J I now regard my Coleman 128c as 'finished' - at least, to my satisfaction. Jean sold me the Aladdin shade a while ago but it's taken me a few months to pop over to collect it. The shade was made for an Aladdin wickie lamp but the overall style and size looked close enough for my purposes. I am extremely pleased with the result and love the glow of the shade when it's lit. I suppose I might stumble across a genuine Coleman shade of the correct vintage but until I do, this suits me very well.
I had everything ready, just needed to put it on. Thanks again Jean, it's now the oldest and most elegant lamp in my collection!