nanoBTS + external Antennas + Repeater

Good morning, I would like to use two directional antennas with a nanoBTS DCS1800. As far as I know, first I need a duplexer to use one antenna both for RX and TX - does anybody know a cheap model? I found only one for 500 Euros. Second, to connect two antennas to the duplexer, I need a power splitter. Can somebody suggest one for duplex usage? Third, to improve indoor signal level, there are plenty offers of duplex repeaters, but the legal situation is unclear because one might produce distortion on ARFCNs different from his own. Again, anyone with experience? Maybe a suggestion for a model with a fixed ARFCN setting? Thanks, Lennart