Genuine JD hoods are not particularly expensive.
I pay $ 125 for them down here bare.
Funny enough the decal kit is almost the same at $ 95
So if you caan live with a kaned hood they are not expensive.
AFAIK no one makes aftermarket bonnets for any mower.
I have done a couple of bonnets,
One on a 100 series and one on a LT
Both were the one piece plastic hoods and under $ 200 with out decals & grills
I am fairly sure that the LT was only $ 125 bare
The only expensive one I have been quoted was for one of the rebadged Yanmars with loose sides so that went down to the motorcycle smash repairer for plastic welding .
I was supprised as a plastic bonnet for a local mower was around the $ 300 mark.