This programming lead should work with all brands (Alpha 10 Max AM-1000, AnyTone AT-5555, Comtex CS-1000DX, CRT SS6900 (SuperStar 6900), Hannover BR-9000, K-PO DX-5000 etc.) and versions of this radio that require the bottom casing to be removed for programming and be compatible with all versions of the programming software. It will be electrically compatible with versions/modified radios that have a programming socket fitted or pins at the modified mic socket, but you will have to discover what wire goes where (if you email me firstname.lastname@example.org with the data for dealer modified sets I'll be happy to include that info here too).
I've added colour to the schematic that was posted to aid circuit tracing (although it was pretty clear to start with). The Yellow, Red and Black for TX, RX & GND are reported as the correct scheme from the original lead.
For the construction you can use strip board, dead bug method or even produce your own PCB if you like. Just follow the schematic. Component layout is not really critical for this circuit, although beginners (and the more experienced) may have to double check polarity / orientation of components.
Once made up check your soldering for bridged connections and wires for stray whiskers. If your construction is small enough it may fit in the shroud of the 9 pin D socket, if not a small box with short leads connecting to the 9 pin socket will work just as well.
The radio end plug (P2) is not shown but you will need to know how it is set out:
A USB to Serial adaptor (using the Prolific Chipset works, so I am told) will be required for PCs without a serial port, the programming software will need the port set to the COM port that the adaptor is emulating.