It's pretty quick, it arrived. It's The Compact L298 motor driver from Solarbotics. I might have some time to do the soldering work this sunday after my busy services in the church this weekend.
It's really compact, I guess it fits ito a hand controller box easily as well, actually, I planned to use it for autoguiding signal, but now I found it's an overshoot, since from Shoestring astronomy, I know their guiding signal is strong enough to push SPDT relay, which should be enough for driving motors. Anyway, it's a learning process, I went the complicated and more expensive route.
Right now the problem goes to the mechnical parts, I guess right now I've at least 3 or 4 workable methods to do hand control and receiving autoguiding signal... I ordered some inline shaft coupling last night, but due to the size difference of the shaft, maybe it would cause big trouble. Also, since the guiding actions are pretty small, I should have very good mechanical construction or else they will be eaten up by backlash, or whatever mechanical imperfection, etc.
Originally, I was think about a motorized focuser, but the accuracy for driving a mount should be way higher, anyway, I'll just move on and the bottom line is, it will be a fun project!