GM, Ford, and Chrysler have had programs to reimburse dealers to provide a free top tether anchor retrofit in many vehices made in the 1980s and 1990s, until top tethers became standard. While some dealers didn’t know about these programs (or even tried to get the customer to pay anyway), it was still a great program and well-known to many child passenger safety technicians. In turn, we would give the information to parents who could use these retrofit kits in their vehicles.
Unfortunately, such free retrofits are not available on many other makes. While the parts exist, the kits can often cost $10 online or even more at a local dealer. Adding to that, many dealers will charge you a minimum half hour of labor and the total can be $40 or $50 or higher:-(