It appears that Ifixit does not sell parts for your phone
If you can't find the parts elsewhere here is an option that you may wish to consider.
Purchase and scavenge the necessary parts from it. Depending on your location the postage will hopefully not increase the cost too much. If this is the case you are unlikely to find buying the parts separately any cheaper.
Alternatively there are more listed here which may suit you better. Scroll down to view.
Here is a link to the Ifixit repair guides for your phone, which may also be of assistance.
Nokia 2115i Repair