It really could be anything in there.. 90% of the time, a creak comes from upper wishbones unless you're a particularly unlucky person like, for instance.. me.
In my case its the ARB bushes, confirmed by the fact that I disconnected the drop links, tied them off and went for a gentle drive.. no noise. reconnected them, noise back... of course, I repalced my uppers thinking they were the culprit first.. on the upside, it turns out there were knackered anyway and the car is handling really well now.
You can try to dose it with Silicon spray but the sway bar bushes are deep in the subframe and very hard to properly get at.. this does work for some people though.. not me. I'm unlucky as we established earlier.
If you have tools, you just need to put the front on stands, get your self a 17mm socket and an allen key (forget the size) and disconnect both drop links.. assuming they aren't rusted on.. cut them off and replace - they are very cheap and will almost certainly need replacement anyway. Before you put the new ones on, go for a spin and see if there's any diff.
All that said, it may also be the lower wishbone.. although that normally makes a knocking noise when steering...
And, I learnt only yesterday thanks to this forum, that the top suspension rubber mounts may also be the cause... I'm not sure how you'd confirm or test that though.
Hope that helps