Does anyone know what kind of AC Adapter this wheel gets? I want to get FF going, but I lost the power cord a long time ago. Thanks!

Its this one, right? As I see all Logitech wheels except G25 use the same power supply, I also own one Driving Force and DFP, tried DFP with power supply with the older one, and guess what - it works. Specifications are same (voltage, output current), also i think this probably goes for the Logitech momo. So any logitech ac adapter should do fine - excepet g25?.

Model: ADP-18LB C

Input: AC 200-240V -0.4A (German Voltage, maybe differs from yours)
Output:24V - 0.75A

Right now I'm comparing the one of the Driving Force and Driving Force PRO, those are exatcly the same, output 24V 0.75A, also model ADP-18LB C.

Whatever you do, don't use other power supplies like I experimented with a few minutes ago, unless you know what you're doing. I also lost my original power supply long ago, so I've been using a 7.5v Radio Shack one meant for digital cameras, which worked, but the force feedback was a bit too weak (takes 5 seconds for the wheel to turn lock to lock; 90 degree turn on each side). Well, I just fried my force feedback trying a higher volt power supply thinking, "oh, the voltage is only half of what these people are saying, so it'll be safe!" It was the power supply that came with Creative T3000 speakers - the only one I could find that fit into the wheel other than a 9volt guitar pedal one which didn't fry it, but made it spaz out. I put the power supply I usually use back in, and sure enough, the force feedback is dead. The wheel and pedals themself still work, and the motor resistance is still as tough as ever, but anything to do with force feedback is dead.

The one that fried it (the Creative T3000 speaker one) says:
input: 120v ~ 60hz 550mA
output: 12v ~ 2.9A

and the one that seemed compatible (but weak) says:
3 ~ 7.5v (it's adjustable and worked with every setting, with the FFB weaker on lower settings) and 2.0A

One thing I didn't notice (AKA lack of knowledge) was that 2.9A thing, and I now suspect that's a pretty important factor, being that much higher than the original power supply's.

Quote from VoiD :

Model: ADP-18LB C

Input: AC 200-240V -0.4A (German Voltage, maybe differs from yours)
Output:24V - 0.75A

Same as the Momo Racing Black, positive inside, negative outside.

The G25 power supply output is stronger: 24Vdc, 1.75A, same polarity.

As long as output voltage, polarity, amperes and connectors are the same you should be fine using a compatible unit, if you find one. In your case it would be 24V, 0.75A, positive inside, but if I were in you I'd wait for some American Driving Force owner to confirm this to be completely sure. The American psu model should however be GAD-SLU-240A8, 110V input, same PSU as Driving Force Pro. Take a look at this for more info.

It's OK to use a power supply with a bigger current capacity than needed. If you find once with, say, 24V and 1.0A then that's usable - the wheel will draw as much as it needs.
Therefore:
Same voltage (24V)
Same or greater current (=>0.75A)
Same polarity (positive centre)