Ok, first thing--have you tried reducing the voltage? In other words using a couple AA batteries instead? You probably need to find a battery box, but, to test, you can (often) hold the batteries together.
If a couple AA end to end work, that's 3VDC (1.5V+1.5V). If that's not enough, you might need 4 cells (which will want a battery box to hold) to give you 6 volts. To get the volts to multiply, you go + to - on one battery to the next. If you connect + to + the voltage does not increase, but the amps available to "do" work will increase.
Once you get the ideal voltage worked out--3 or 6 volts, consider going to a C or D battery. LEDs are not very energy hungry, but a deeper "well" is its own reward. The battery box then sets in the base (where the increased weight can be handy).
I really like to use the supporting pylon as a condutor, even when inside another tube, as only needing the one wire threaded is simpler.I've alos used an RCA connector as a mointing point, too.
Now, if you are keen, and since there's no longer a Rado Shack on every corner, you might want to google "motion detector switch kit." RS used to stockpile little teaching kits for simple electrial circuits (photocells, rheostats, IR detectors, etc.) which were hugely handy for having all the parts (and instructions) to make one on the fly.
Becasue few things are as cool as models that "come to life" just becasue you are nearby.