The small switch or any other swith can be found at a specilazed spare electronic store, probably at Radio Shack. If you don't fin one, try to get one from an old electronic device like the reset switch of an old computer.
The new switch needs to be connected with the wires to the connections of the actual remote switch.
335i E92 / Sideral-Gray
/ Coral Red
/ Aluminium / 6M / Winter Pkg / DIY HomeLink
K.I.S.S ...Keep it simple stupid