"I am also concerned about these spark plugs that I have bought, they are the RCEXL ones and don't have the groove cut in the flats, that the little springs connect to....I am wondering if the plug caps are not seating properly. That also makes me worry that if I ever lose one of the spring clips, would I be able to get new ones somewhere.....seems nobody carries these....which makes me nervous..."
You could trim some material off the bottom of the sparkplug caps (some, including myself have done this) so that the spring clip sits under the hex on the sparkplug, or perhaps you could cut a groove into the sparkplug hex using a dremel with cutting disc or similar.