score:17
I'm only aware of one surviving iron coupling-sleeve that joined the two halves of the sarissa spear-shaft. The discovery was reported in the 1970 paper Sarissa by Manolis Andronicos in the journal Bulletin de Correspondance Hellénique, (vol 94-1 pp. 91-107). The iron sleeve is shown in figure 8:
and the measurements that will be of particular interest for you are on page 98:
(fig. 8). Douille en fer. Plus étroite au milieu, elle s'évase aux deux extrémités, présentant ainsi un profil légèrement concave. Elle est de section circulaire à l'intérieur, et polygonale à l'extérieur (à quatorze côtés). Les deux bords de la plaque n'ont pas été parfaitement ajustés, de sorte qu'il subsiste entre eux, du haut en bas, une fente, qui est plus large sur les 3/4 de la longueur. Long. : 0,17 m. Diam. a : 0,028 m., b : 0,032 m. Épaisseur de la paroi a : 0,002/0,003 m., b : 0,003/ 0,005 m.
Google translation:
(fig. 8). Iron socket. Narrower in the middle, it flares at both ends, thus presenting a slightly concave profile. It is of circular section inside, and polygonal on the outside (with fourteen sides). The two edges of the plate have not been perfectly adjusted, so that there is between them, from top to bottom, a slot, which is wider over 3/4 of the length. Long. : 0.17 m. Diam. a: 0.028 m., b: 0.032 m. Wall thickness a: 0.002 / 0.003 m., B: 0.003 / 0.005 m.
(The original paper was written in Greek, but the version linked above is a French translation. I'm not aware of an English version)
The problem with metal artefacts is that they can be readily melted down and re-used, so there is no way to know how often they were used in practice.
Another paper that you might find helpful is The Macedonian Sarissa, Spear, and Related Armor by Minor M. Markle, III, published in the American Journal of Archaeology (Vol. 81, No. 3 (Summer, 1977), pp. 323-339) which is available to read free on JSTOR.
A discussion of the dimensions and weight of a Sarissa (based on 'the well-preserved remains of both a Macedonian spear and sarissa of the late fourth century B.C.") appears on page 324. The diameter seems to be rather less than the 4-6cm in the paper you cite in the question though.