Matt, the zip you are showing came later, i think. The one that is correct (I think) for late Pagodas does not have the fixture you use to anchore it in a hole in chassis - those types of clamps with various length I have e.g. in my 1991 W463. I am sure they were used earlier, but I do not think for W113 (not sure though!).
The one I posted the poor picture of does not have that fixture. It is a simple ribbed plastic strap, re-usable.
I am not aware of any plastic tie near the fuel lines (does not mean they were not there, I just did not find them). i posted the number as you asked about it. But the only "clamp" there as per parts list (other than the hose clamps of course) is the metal clamp Shvegel is describing and you have on my photo. It screws to the floor somewhere (do not remember exactly where) and holds fuel pump-fuel filter line. I will double check that.
I can give you part number for the clamp (or tie) with the fixture that you show when I am back in my garage - I have them, can give you length too.
If you want to have the fuel pump cover correct, please look up in the Technical Manual which one is correct for your car.
There are also threads, including one I started, talking about the fuel pump type, type of cover and fuel lines set up. I have picture of mine, but it is a short style for late 280SL.
So there is a decision point:
1. You want to stay with what you have (that may not be pure and correct) and you need a part number for the tie you have (strap with fixture) - I can give you part num ber and description end of week when I am in my garage or I can give you 80% correct part number later today from EPC. Or just go with what you received from Tom, which is, I am sure, the correct part number of tie you asked for.
2. You want to re-create the exact and correct set up and cover of your fuel pump (probably long style) - then a bit of a study and questions will determine what parts you need. If you already have a short style pump, you probably need to stay with what is correct for short style as far as cover is concerned.