'arlon' - I am not totally sure of your question or of the rear-sight that you have right now.

Maybe you have the '3-notch' model 1898 sight or a model 1902 sight without the 'swing-up peep'?

In either of those cases, a later model 1902 leaf and eye-piece can replace the original parts. You simply compress the leaf spring and lightly drive out the pivot pin, change the sight leaf and reassemble.

The model 1898 and model 1902 sight bases have different heights and different leaf springs. However, the actual leaf/eye-piece part can be switched for 'Shooting Purposes'.

---