can you buy a power cable from mac studio display

It is not user removable and will void your warranty if you do. Yes, YouTube has videos of people yanking on it to remove it, as they did with the HomePod mini when it came out. Tinkerers always do stuff like this and sometimes they wreck things. The fact remains Apple states it is not user removable. And no, you cannot buy a replacement cord anywhere as it is not any kind of standard connector and Apple will not sell you one. But hey, it’s your Studio Display, yank on the cord all you want.

Not currently, no.

Its technically not user removable as it requires a special tool to unplug it safely from the studio display.

If you search the Internet, it seems, that Apple is able to remove the cable and replace it with a new one.

You should contact your nearest Apple Store about that:

Apple - Find Locations

Why would you want to? It’s not user removable.