You're misusing terms. The KI-214, KI-209, and KI-208 all include a internal VOR-LOC CONVERTER (they don't have any "receiver" in them). The KI-209 should work everywhere the 214 does. You specifically do not need the KN-72 which is an extern VOR-LOC converter with either of these indicators. I've never heard of a KI-210, I presume you meant the KI-201.
Given the combo of the KI-214 and the KN-75, I suspect he has either a KX-170 or 175 (hopefully the B models as the earlier ones aren't likely to be legal to transmit with anymore).
The 208 won't go with anything with a glideslope receiver (internal to the radio or external like the KN-75), it lacks the glide slope needle
The indicators that work with the KX-170/175 and the KN-75 are the KI-209, 209A, and 214.
The ones that work with out the glide slope are the KI-201, 208, and 208A.
These are all available and as Jim says all still serviceable.