1:50 Dragline

[MattDk]

Yes that was the video I was referring to.

Here you can find one optionhttp://www.magomhrc.com/en/search?controller=search&orderby=position&orderway =desc&search_query=Ring&submit_search=Search

Another way is this http://www.adafruit.com/products/736

If the mini jack were to work you might have to skip the screw in the middle and just hope the mini jack will keep everything in place.

Doing two servos will not make it that more advanced, it is actually only one more wire, since you share power and ground, between both servos.
You could choose to put the servos in each end instead of next to each other.

If you cut the connector between both sides of the wheels and keep just enough metal to put something like a pinio gear without the gear "cant remember what it is called" to keep the wheel in place. Then you can mount the servos at each end.

I can't figure out how much space you have in the undercarriage, but I have converted a normal servo into driving one of these motors instead, http://www.goodluckbuy.com/micro-dc-...-6v-1-100.html they don't make as much noise as a normal servo.
The conversion is quite easy, I just can't find the link that I followed.
I would also say that if you have the space inside the cabin to use this kind of motor instead, you could have a very powerful low noise setup.

/Mario