Steerable Nosegear. Here's a link to someone who has done it successfully
These ones work off the rudder servo. You mentioned something about not using the rudder??
Or you could buy servoless retracts from Sussex Model Centre
Ordering from the States isn't too bad, but at these prices they stop your package on arrival in UK and charge you VAT on top.
HobbyKing in the US have the best deals, and Grayson Hobby will give you good advice if you email them.
I'm not actually speaking as an expert. More of an expert on belly landings in rough fields.
Keep us posted. It's an interesting project.