There are mITX/mATX cases that are small/portable and very functional for water-cooling as well. I use a Raven RVZ01 (see also FT01 for less aggressive styling

There are mITX/mATX cases that are small/portable and very functional for water-cooling as well. I use a Raven RVZ01 (see also FT01 for less aggressive styling) and I have a 120mm AIO in it.