I don't know first-hand, but, FWIW:

Joe Poyer in his book, "The American Krag Rifle and Carbine", describes the front carbine swivel-screw (for the 'saddle-ring bar') as being .60 inches long and the rear-screw being .885 inches long.

Poyer says the rear ('saddle-ring bar') screw is the same as the butt-plate tang screw.

It appears the rear carbine 'saddle-ring bar' screw also has the same dimensions as the rifle 'butt sling-swivel' screw(s).

A pair of Krag (rifle) 'butt-swivel' screws, with one shortened to .60", should do the trick.

Grandpa's Gun Parts (in KCA Classifieds) has these screws on sale for $3.00 each.

Nomenclature is always a problem for me. I have modified my original post slightly and added verbiage to try to make things clearer.

(I was not quoting Poyer directly. Noticing that, 'rifle butt-swivel screws' seem to have the same dimensions, was my observation and experience).

To be succinct - Krag carbines (usually) do not have 'rifle sling-swivels'.

The Krag 'short forearm' carbine stocks, (for model 1896 and model 1898 carbines), normally have a 'saddle-ring & bar', on the left stock wrist area.

(This was used, with an across the chest, wide leather 'carbine-sling', with a 'roller snap-hook' device, that allowed the carbine to be brought into action and not accidentally dropped, while mounted).

I believe, a pair of rifle butt-swivel screws can be used to attach your 'saddle ring and bar'. The front screw needs to be shortened to .60 inches. (I suspect 1903 Springfield butt swivel screws would also work).