Should be possible. A quick look suggests that for a leviathan soundbar a power supply brick will have to output 18V at 2.6A, for an input of 100 to 240V. I assume you are UK/Ireland. Both the brick and the soundar itself will have electrical output and input specifications on them, you will need to check to make sure. A quick look at what's availible in china, suggests that an output of 18V and 3.0A would do. Still abit of reading to do there.
Question: why do you need one? Bought a soundabar without one? Or the old one died? Hopefully it is the power supply, and it didn't kill the soundbar, or it wasn't a short in the soundbar electronics which killed the power supply.
Electronics are funny at times, but it shouldn't be too much of a hassle to getr a generic power supply which would work.