I thought this may be worth investigating. It is not very easy to source parts required to build AIS receiver (for tracking ships). Maybe ModMyPi could consider stocking the following:
* 162 MHz filter
* VHF/AIS antenna
Obviously you also need receiver itself and cabling, but good news here - you already stock them! FlightAware Pro Stick (orange, non-filtered) should do the job. I am currently using regular "no-name" DVB stick in my PoC and it works surprisingly well - Pro Stick should take it to the next level. Finally cable you stock for ADS-B should be just renamed to ADS-B/AIS
I am currently awaiting delivery of the 162MHz filter, so after testing it I will be happy to privately share details of where I got it (assuming it works well). As for VHF/AIS antenna, I am still looking as none of the antennas I found so far fit in my current budget (after combining antenna cost and shipping). For now I am using DIY in my PoC and I plan to build next iteration of DIY for my first "production" system, but if ModMyPi stocked antennas with reasonable shipping costs, I will be first in a queue to purchase it. Again I can share privately supplier that have them at reasonable price (before shipping from far away gets applied).