Oh my goodness I just ordered that weasel ball. That looks amazing, and will definitely keep Lexie entertained for quite a while.
I also have done the stick, with a rope and a toy on the end, and it uses up quite a bit of lexies energy. I am studying for the cpa test right now so a lot of time I will just be sitting at my computer and hold that in one hand and she goes at it for a while. All I have to do is move my hand every once in a while.
I also have a remote control rat - I got it as a white elephant one year, but it has ended up being amazing. Lexie will chase and attack it until I make her stop and put it away. I will say this definitely encourages the barking, because of course they are going to want to bark at it. So that may be something too consider if that's an issue for you.
One last idea I do with Lexie is I will get a toy or treat, show her it, then go hide it somewhere - this works best with treats because they can smell them. Then I say "where is it" and she goes looking for it. Very fun
I think I may try to do the obstacle course idea. Lexie often does this on her own, she just goes crazy and runs laps around my living room following the same pattern each time.