Honda VTX 1800 Forums
I know of 2 rear shock bolt covers compatible with the 2004 VTX 1800R:
Show Chrome Accessories (Big Bike Parts) Rear Shock Bolt Covers (4 pcs) (Part Number: BBP-55-115)
Kuryakyn Rear Shock Top Cover (Pair) (Part Number: KY-8261)
But I replaced my stock shocks with the Progressive 412...