A shame caselabs isn't around any longer. Not actually finding any of the smaller cases in stock anywhere. I think the trend for SFF is to make 240mm radiator the base size, usually top and bottom with the computer sandwiched between them.
If you can find a Cooler Master HAF Stacker, that would probably be the easiest I can think of. I looked around for other low volume chassis, they just don't support a 360mm radiator. Other option would be to look at Micro ATX towers that are small.
Keep in mind you will want a beefy power supply to go with a 3090, 850W is the bare minimum recommended.
PCPartPicker Part List
CPU: AMD Ryzen 7 5800X 3.8 GHz 8-Core Processor ($419.00 @ Newegg)
CPU Cooler: Noctua NH-L9x65...