I do a quick search for you:
http://www.inspirepilots.com/threads/t-motor-carbon-fiber-props.10091/
Replacement Props time !
Your question about the warranty is not so easy. The manual doesn't say that you are not allowed to use 3d party props but of course, if your bird goes down due to cheap, wrong mounted props your bird is out of warranty. But that is the same for the original ones, if you have used damaged props or you didn't mount them properly -> you fault! Even if you did everything right with the DJI props it is hard to proof that it wasn't your fault!
CF props perform usually better than the plastic ones, less noise (depending on the props), better & faster reactions from the bird etc. etc. BUT don't safe money on the props!
Here is a link to Lynh Phans shop with CF props and special adapter plates for the Inspire 1:
Lynh Phan Global Industries
250 bucks for a set of adapters and props is insane bu it is worth it...
Chris
just my 2 cents...