How can I fix this sporran?

[Troglodyte]

A common problem with press-stud fastenings...

My preference would be to remove the remaining part of the existing press-stud, and replace it with a monk-rivet (sometimes called a capstan-rivet) in either brass of nickel. The leather tab with the hole where the missing part has been will need to have a small slit cut along the length of the tab, in the centre, of about 1/4 inch, to allow the tab to pass over the new rivet.

The monk-rivet is a two-piece item, with the rivet being held in place by an almost flat screw, which will use the existing hole when the other part of press-stud is removed.

Most leather-craft supplies have a range of sizes and styles, so you ought to be able to find something that suits.

Alternatively, a shoe-repair or even a dry-cleaners can replace the press-stud if that is what you prefer.

Good luck..!