Harley is pretty broadly licenced -- this works in your favour inasmuch as there's a huge selection and variety out there, but can be an aggravation inasmuch as it's going to be spread across many different suppliers.
As with a lot of other licenced product lines, one of your better bets is to get out there and find stuff offline, and track down the supplier -- if there are any sizable bike shops in your area, or rallies, you should be able to run up a ton of leads. That is not to say that there aren't any online or listed in Salehoo; I'm sure there's a ton. But being able to see the stuff on the shelf, see what catches your own eye and what kind of price points it's fetching in the real world is useful (plus fun, if you happen to be into Harleys and Harley people.)
Bear in mind also, if you have an idea for a Harley-themed product, HD is very proactive in forming licencing agreements (one reason why there are so many products out there.) Their licencee requirements are on the site -- the HD opportunity is huge because anything that passes through their licencing department is in turn promoted to their retail network as potential shelf stock (not just motorcycle dealerships either; Harley has stores that are just clothes & accessories, and other operations as well.)