I've done a load of cantle switching over the years.

My advice would be to pick up a vintage full length horsehair sporran on Ebay and put your nice vintage cantle on it.

A 6" wide cantle is fairly standard for 20th century adult sporrans. I've had a number of cantles over the years from the 1900-1930 period and they're usually that wide.

In the 19th century cantles tended to be somewhat wider. I just sold a 19th century cantle that's around 6 1/2" wide.

I actually have a very nice, new condition, full size white horsehair sporran made by Janet Eaglton that I could sell you. I was thinking of keeping it but I'll probably never end up wearing it. Your cantle should pop right on.