Odd Need

A customer who bought a ScopeRoller set in 2005 needs a replacement set.  The plastic of the wheels is corroding away.  The vendors charges a substantial fee for tiny orders.  I found the third hollow pin caster I need on eBay; the other two I found next to a pterodactyl.  But there is a 3/8" to 1/2" adapter that I need to complete this 3rd wheel assembly.  Any idea where I might find such an odd bushing?  It doesn't rotate; just allows a 3/8" bolt to not slop about in a 1/2" hole. Never mind, found some in the Paleozoic layer.