You can't buy either of these, but Classified Moto might let you commission your own. The dudes behind this custom bike company collaborated with the dudes behind The Walking Dead to construct a pair of identical motorcycles the show needed to replace Daryl Dixon's lost chopper.
According to Classified, The Walking Dead's primary goal was to have a set of bikes that ran flawlessly, started every time, and didn't flip Norman Reedus over their handlebars. Because the irony of a zompoc survivor and society's most badass walker slayer dying in a freak motorcycle accident just would have been too great. So the company started with 750cc Hondas from the 90s knowing they're reliable and have widely available parts. They then swapped out the front end and wheels and painted the engine components so that the overall aesthetic was a bike that looked like it was pieced together from a lot of different bikes.
The finished product has a Yamaha YZF-R6 front end, front wheel, and front brakes, and a Stock Nighthawk rear wheel. Both tires are Kenda Big Blocks, "big knobby dirt bike tires for good off-road handling and a super aggressive look."
Check out more photos and a complete recap of the Walking Dead bike building process on the Classified Moto website.