I don't know of any major pre-built PC sellers (Dell, HP, Lenovo, etc.) that would use a Seasonic PSU. I think most of these companies use their own version, much like their own motherboard.
Maybe you can try CyberPowerPC or iBuyPower, which are companies that customize builds. These companies might have that Seasonic PSU.
You can also build your own with a Seasonic PSU. If you want an Intel CPU, go for the Z490 motherboards. If you want an AMD CPU, go for the X570 motherboards.