I have a brass single edge razor from Italy that I'm looking for "Single edge slide through razor cartridges". I can't remember what I used when I used it years ago. I thought maybe something by Gillette, maybe a TrackII.
You are describing (I think) the Wilkinson "Bonded Shaving System" which has no modern equivalent to my knowledge. I have been using a Trac II razor which is the closest thing on the market to that style.
It has to be a trac II. I don't know what country you're in but CVS sells a trac II astra combo cart that will fit it. Two blades on it not one, though.
I bet it was trac II. This set was bought in Italy in the early 90's. I remember the cartridges came in a square clear flat plastic container with about 10 cartridges. You slid the razor across and pull it up with the cartridge affixed to the razor. I do live in the U.S. And I have a CVS near me. Again the razor is not a Gillette razor. It's just a brass razor.
Well, sometimes ya gotta pay to play. When you get back from CVS, please let us know if those Trac II carts fit! I really want to know! Good luck!