Quick and easy, check with
http://car-part.com. Check within your local area. It may be pricey, but recycle yards will negotiate on the pricing. Next, check with your local Jeep 4wd club. KC Jeep Club has several members with the JK. I know one was selling its hardtop at one time. I believe the sale funded the lift and tires that are now on it. Also check with your local CL listings. If you are couple hours drive from another major city listing on the CL, check that out. Same for Jeep clubs. Lastly, check your JK boards on major forums.