I am 90% sure it is Corlanes that can bring those in. They are not cheap - you might be able to pick up a whole chassis of the EE for about the same price.
If my memory serves the guys at KRG are big fans of the TRG and the Whiskey 3 Chassis butt stock can be attached to a TRG.
I have had a TRG and a KRG W3 but not together. I would say that adding them together would make things a lot nicer.
Recently, KRG announced they are making a W3 that will accept the TRG and it can even run the CTR mags.