That being said, are actual Mode A only TXPs even still being manufactured?
As far as I can tell, no. You notice that all recent transponders say things like "On" and "On + Alt" rather than "A" and "A+C". I asked the CAA about this and they said that all transponders have to be at least A and C.
(Which I guess also implies you wouldn't get a radio licence for an older non compliant model).
Thing is there is a vast ammount of literature that is wrong about TCAS and Mode A, but usually its "two wrongs make a right" on the end result so its
almost an academic distinction.
pb