any hardshell foam-lined case will work. the isms system shipped in a pelican 1700, which was enough for 120hp of eurorack, a 128 grid, and several other bits of gear. check with the airlines to verify their allowed carry-on size.
are you taking an arc and a complete eurorack system, or just a few loose modules? the latter can probably be kept in their cardboard boxes and stuffed in a backpack.