I am a motorcycle enthusist (aka biker chick lol) The only way to get the actual harley logo is to harvest it from other places such as sheets and curtians.Now there is lots of "biker" type fabrics out there if you search ,it just wont have the typical what they call bar and shield logo.
I have ridden a harley since 2000 and have traveled as far as south Dakota on mine, I have spoken to many harley people and even emailed the company , unless something has changed recently they have not released the copyright to any fabric manufactures,of course this was a year or so ago that I checked.
Go with some of the motorcycle themed fabrics, die hard harley people are getting away from displaying the harley logo for many reasons .