Any road bar shifter you like. Though some will say that Shimano road bar shifters will not index properly with Shimano mountain bike front derailers, rear derailers are fine. I don't know the Trek T100 but if it has a quill stem, you could use stem shifters. You could get some Paul Thumbies for road bars.
If you don't have the bars yet, you could get Trekking bars and use your LX shifters. Or get bar ends, they even make some like the drops on drop bars.