You want to buy parts & assemble one?
http://store.nkcelectronics.com/arduino-runtime-board-rev-b.html
will do all an Uno does (except accept shields), you use an AVR ISP programmer to load code into it.
Or connect to the Rx/Tx/Reset pins & use FTDI type adapter for serial downloads after the bootloader is installed.
You want to build one from scratch? Here's an ATmega1284 test board I have.
I offer the same as an ATmega1284-based PCB that will also accept shields. You buy parts & assemble.
Update your IDE with the 1284 files here, select Bobuino as the board type.
Use an ATMEL AVR ISP for loading the bootloader.