I guess buckstitch is another name for thonging
Buckstitch is indeed a type of stitching which uses thong/lace.
The links look like thonging chisels and Black Sheep's pics look like they've been made with ... thonging chisels
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Craftool do make Pricking Irons - but call them 'Craftool Diamond Hole Punches'. They're available as a single prong and in two different four prong versions (tines either 1/8" or 3/32" apart).
I use the 1/8" version - they work well, but be prepared to check and realign the tines as you're going when using on thicker leathers.