Sorry, should have looked at your tiny picture at the Roosevelt wheels. Due to the way these wheel mount, running with 3 bolts per nearly 40 year old wheel is not a good idea.
It can be hard to find that type of bolt of late. Check with some of the other forums to see if anyone has a few laying around.
http://www.mirafiori.com:8080/forumdemo ... ener.Cars_
You might be better off going to threaded studs and lug nuts.
The Medium Mag with Washer may work on the following link but you will have to measure what you have to know.
http://www.wheelcomponents.com/lugnuts.html
I haven't had any luck finding new ones, I'll post back if I do.
Found this article on making some, you might contact him:
http://www.kendickson.com/car/frwheels/wheelbolts.html
All other references were quite old on Mira Fiori, those guys would be pretty likely to have a few.