Are you looking for a list of part numbers of what is on the bike already, or a list of accessories that you can buy? If the second, your dealer should have a accessories catalog you can take, just ask them.
You can also go to www.harley-davidson.com and look up your bike model there and get an idea of what parts are available for purchase or upgrade.
You can buy the parts catalog, I think it was about $40. I also got the service manual and electrical manual at the same time total for all 3 books was a little over $100.
You can look up accessories on-line at harley-davidson.com.