The seal run/spacer is a Lotus only part. Though you could easily make one from R16 or R17 half-shaft, inner CV joints.
As you suggested, I bought 2 x used drive shafts from Renault 16 in Holland. €75 each plus import tax (VAT @ 20%).
When you cut the inner rubber gaiter covering the CV joint, lots of smelly oil comes out all over the place, 4 large ball bearings fall out, and the inner part of the driveshaft falls away very easily.
The spacer is 36mm in diameter and about 11.2mm thick, but the spacer I am using for a pattern had 1.1mm of shims next to it. The inner part of the driveshaft is also 36mm as you would expect, and the length of the inner splines is about 44mm so I should be able to get 3 spacers made from each driveshaft. Thank you for the tip JBC, it seems we can make unobtainium with a bit of ingenuity.