Try a should bolt from McMaster (
www.mcmastercarr.com), like PN 91259A106. These make perfect dead-axles.
If it's a live axle, McMaster has numerous bearings for 1/4" shafts, including this aluminun base-mount bearing, PN 5912K1. I would still use a bearing like this with a shoulder bolt unless you have a snazzy axle already.
"McMaster Carr has EVERYTHING!" has been my team's philosophy this year because we don't have a machine shop available anymore.
Edit: Coffeeism knows what's going on...
