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...