'kolhoznik' - Welcome to the KCA Forum. If you post some photos of your model 1899 carbine, members can provide better suggestions and guidance.

IMHO - A carbine in the 25X,XXX serial number range can have any of the carbine rear-sights you can find and prefer.

Your carbine likely started 'life' with the model 1898 'three-notch' Dickson sight. These were later discontinued and taken off.

Krag carbine hand-guards are 'sight-specific'. Initially, the carbine hand-guards were identical to rifle hand-guards for a given sight model.

The sight-guard 'humps' on carbine hand-guards came later.

Probably the most important thing is to have a pleasant match of wood and metal color, patina, &  finish with your 'new' replacement parts.