72 Shoulder harness seat belt retainer ?

I want to replace my (I'll try to describe it since I don't know what it's called) shoulder belt retainer that holds the belt in the top of the seats. If this isn't there then the belt would go through the seat. They are all plastic like and all black. They are shaped like a "T". You can buy them but then how do you get them over the buckle on the belt. A long time ago I took mine off since they held the shoulder harness in and when you pulled the back of the seat forward the shoulder harness got in the way of putting things in and taking thing out of the back. Now I want to replace them but can't figure out doing it without destroying the retainer. How do you get them to expand to do over the buckle without recking them.

They came in colors other than black depending on year and interior color. As far as getting them on. Warming them up(hair dryer will work), patience, and cursing will work most of the time. Mostly cursing for me. These were the only parts holding up my '70. Every supplier I spoke to was out of the medium saddle that I needed, so I used some black ones we had just to get the car on the road. I have been in Atlanta for several months and will be going home in December. Hopefully my saddle ones will be waiting for me.

Please post a picture or link to the part. I don't remember ever seeing them. I have a freind trying to put shoulder harnesses in his car that never had them.
Thanks

I don't have the info with me here in Atlanta, but when I get back to NJ in 3 or 4 weeks I will post the part number. Without them the shoulder harness will just pass through the seat back.