Are you wanting a tube or more traditional style? There are a couple people who sale tube style bumpers over in the vendor section at
www.ck5.com
Kennesaw Mountain Accessories makes a more traditional style front bumper. Burt4x4 uses their front bumper on his K5 and it looks like a good bumper. They are a bit expensive and I think you would want to talk with Burt about his bumper.
The 73-87 bumpers are very similar and they can be used but I've read they have a slightly different shape that gives a bit of a gap at the center of the bumper area.