I believe this is what you need. The number in your picture does not show up in the JD parts catalog. It may just be the casting number. M48661 is the front PTO pulley for the 400, 420, and 430. I just replaced mine.
The JD part is $321. This company sells a new aftermarket pulley for $238.
M48661 John Deere Pulley M48661 | Same Day Shipping | Free Returns | 60 Day Warranty | Fits: 400420430
flipmfg.com
Anything you find used will probably have the splines half worn down already, so just keep that in mind if you find a used one cheaper.
My father-in-law and I tried pressing in a steel splined coupler into the old pulley, but the cast iron pulley cracked when I had it welded. I still wonder if it could be done if more care was taken by the welder. In the end, I found a used one that was good enough for my use.
My pulley wasn't nearly as worn down. How are the splines on the shaft?