Diopter needed to fit early type HW55MM.

[zooma]

I am looking for an HW dioptre rear sight to fit my early type HW55MM match rifle.

The type I need is to fit the older 13mm wide scope rails, and not the 11mm size used on the newer versions of the HW55MM.

I do have an 11mm HW diopter sight from a later model, but some of the pictures I have seen suggest that at least some ( if not all) of these early type 13mm types of sights may be of an earlier design, although some may well be the same as the newer 11mm types apart from the width of the fitting - but any expert input about this would be welcomed, and any type that fits would be welcome!