Serit tuner
As of February 2017 the Sharp and Samsung tuners are no longer available and the Minituner project will use a tuner from Serit which cover from 140MHz right through to 2650 MHz without the need for any upconverters.
Filters and pre-amps
The wide band coverage makes building a receiver for 146 or 437 much easier, although you will need a pre-amp followed by lots of filtering for each band, just like the Sharp did, and probably followed by a Satellite line amp from ebay as the Serit has less gain than the Sharp.
Filter designs are available here
Adapter card
Also, due to a different pinouts from the Sharp NIM, the Serit tuner will also need a simple adapter board to enable it to be plugged in to the Minituner standard hardware - Brian G4EWJ has designed a PCB and the board with a full set of components plus the Serit tuner is available in the BATC shop.
Full instructions on how to build the kit are available in this pdf: