I am building my own antennas to connect to the KrakenSDR. Where can I get the male SMA Antenna input connector?
SMA is a standard connector. Any connector which is described as SMA will fit.
Your own array is definitely the way to go for specific bands. You can find high-quality male SMA crimp or solder connectors on sites like Mouser or Digi-Key (look for LMR-100 or RG-174 compatible ones depending on your cable). Just a heads-up: make sure the cables you use for the 5 inputs are phase-matched (exact same length and type), otherwise the direction finding accuracy will be all over the place!