Hey Jock,
Hobby King has some 4" diameter "warbird wheels" which look very similar to the Robart units but are about 1/8" narrower. (1" wide compared to 1.125" wide) I have a set and will use them instead if I am unable to locate the TF P-40 wheels. I am not fond of the tread pattern but may see about grinding that off. Maybe the HK wheels will work for your Dauntless as well?
http://hobbyking.com/hobbyking/store...2pcs_Set_.html