https://www.ekwb.com/solutions/kits/liquid-series/
It's what I think is the best 120mm single fan kit available. I use a 240mm version of an EKWB and it's great. The only way to best this is to upgrade the DDC pump to a D5.
This is however more expensive than an AIO kit such as the Kraken, Corsair, Kelvin, etc...