I came across this while searching for an entirely unrelated part. I thought I'd share it as I know that diy ATC mods are of interest to some people here.
This is apparently a screw-on ATC adapter to turn a regular ER11 MTC China spindle into an SK15 ATC spindle:
USOVO.de
I knew they had these for Kress routers but I haven't seen them for other spindles before. The adapter and tool cart look affordable - espiecially if you already have the gear for the pneumatics.
I wonder how well they work...