I think it is true that Knight rifles has gone out of the business of making new rifles.  

As I understand it they ahve sold the warranty and accessory portion of their business to someone else.  I haven't noticed the availability of the orange disks but I have a Knight rifle that takes the red disks.  When I heard that they were going out of business a year or two ago, I bought some extra packs of the red disks and have been careful to re-use them when I am on the target range rather than throw them away.  They loosen up a little over time as the plastic expands with each firing but re-using them they work just fine for use on the target range. 

I save using the new disks for when I am actually hunting and want to be sure that the ignition is kept in place and stays tightly waterproof.  At this rate of usage I have enough for a lifetime with 100 or so disks on hand.

Can you mail order the orange disks from somewhere like Cabela's?

Actually, they are now back in business after a short transition. Here is one of the articles I found referencing it....

http://www.thefirearmblog.com/blog/2010/03/30/knight-rifles-back-in-business/

Thanks guys, i actually had time to find a website and a phone number for them on the net today. I ordered 500 ORANGE discs and she (Robin) said she could sell me a new rifle too. I will likely order another 1000 discs very soon, kinda like insurance cuz i love shooting that gun. Thanks Again Guys

http://www.knightrifles.com/

 I ordered the orange discs , somewhere along the line knight shipped red ones. So i called and told them of the mishap, and offered to send them back and they could ship me the orange ones, they told me that they were sorry and to KEEP the red ones and THEY were sending me the orange ones AT N/C. Thank-You Knight

 Maybe i should go buy a new knight that will use the red discs now, seeing i have 500 of them

I never imagined they would ever do that, it impressed the hell out of me. I would have no problems buying a new knight rifle if i ever needed a new one, but for now i will stick with my old one.