Roger,
The nose tire and tube on the Long-EZ are size 2.80/2.50-4. The meaning of this designation is as follows: 2.80-inch tire section width, 2.50-inch tire section height, 4-inch wheel rim diameter.
Aircraft Spruce and others sell a McCreary (now Specialty Tires of America, STA) 4-ply tire with zig-zag tread in this size.
Another option is the ribbed tire (looks like a standard aircraft tire) by Aero Classic. It is available in 4 and 6-Ply versions from:
http://www.desser.com/
The 4-ply should be sufficient for a stock Long-EZ. You will have to take the wheel halves apart to get the tire off. Be sure to deflate the tire before doing this. On reassembly, coat inside of tire and outside of tube with a dusting of talcum power; it will reduce friction between the two. Use care not to pinch the tire between the wheel halves on assembly.
To find the bolt size needed for your nose gear axle, measure the outside width of the fork at the point where the bolt goes through. Measure this in fractional inches. This is the "grip" of the bolt you need. Go to the Aircraft Spruce web site. You need a 1/4-inch diameter bolt, so search the site for AN4 bolts with your grip length.
http://www.aircraftspruce.com/catalog/hapages/an4.php
Cheers,
Kin