May try to find original pre64 1-1/4" swivels at some point on eBay, etc.
Gus, I've been known to use the old military leather slings like that one:
However, when I'm packing around my heavy boy Ruger M77 MKII 338 win mag during elk season, I opt for a light comfy old sling like this Uncle Mike's:
One thing worth mentioning is, I stay away from the new uncle Mikes slings now because they use plastic hardware instead of steel like the older ones (one pictured above). I also keep a couple military type slings ready for the hunt and don't store them with my rifles. Most of my pre 64's still have the original sling swivels, so the leather slings get thrown on just before I go hunting.
The leather Montana slings work well. They're easily adjustable and don't have any metal hardware if your worried about the stock.