StopShot gets $45 for their camera shutter cables. I bought one of their cables for a Nikon D300, to get started, but balked at the expense of a second one for the D70S. Yet I wanted to often use the D70S for playing, to minimize the thousands of shots on the D300.
I tried to go cheap to make one, and I bought a MC-DC1 equivalent remote shutter (for Nikon D70S) on Ebay for $5.50, including free shipping from Hong Kong (these are plentiful from $4 to $10). Just search Ebay for "shutter cable" and your camera model (for example, like These), or if for Nikon, perhaps for the appropriate words MC-DC1 or MC-DC2 or MC-30 (Nikon versions of this).
The Nikon MC-DC1 is for Nikon D70S and D80. D90 and D5000 use a MC-DC2 (camera manual says which, in Other Accessories section). The Nikon D300 family uses the 10 pin cable on MC-30 remote. There are similar inexpensive Ebay remote buttons to provide the connector, and HERE and HERE is info about the Nikon 10 pin assignment.
All you want from this remote shutter switch is the camera end connector. You only use two wires, on the shutter pin and the ground pin, to connect to the StopShot RCA connector. I do wish StopShot used a 3 pin shutter cable, so it could do the half press to reset the sync state for each shot.
It took 16 days to receive it from Hong Kong, but it works great, does what it should, and well. But I only wanted the camera end connector. My plan was to cut off the button, and attach a RCA connector for StopShot (spliced from a TV video cable, or an old audio cable). Problem was, how to convert from three wires to two wires? I can tell you that there are several ways to do it wrong.
Here are the innards of this third party MC-DC1 remote shutter (to be discarded): That is a green ball point pen behind it holding it up.
Problem was, the terminals are marked wrong. I think that is common, and I doubt I could mark them correctly in Chinese either. The order is right, but they are all shifted one place.
Using an ohm meter to ohm the action of original button (far right), it was clear that half press connected blue and white, and full press connected all three. However, going with that knowledge with the original marking produces unacceptable results. Some of these remotes instead use three bronze blades to progressively short the wires together, but same action.
To understand it, it was very important to also ohm to the camera hot shoe metal frame, which showed the bottom blue wire was in fact ground (knowing this is key). This makes top white wire be half press (since it does), and middle red wire remains to be full press. So leaving white half press wire not connected, and connecting red and blue to the RCA connector, works great, and saves $40. Easy and obvious, after learning which pin is ground.
Then the wiring to attach the end of an old RCA cable (from audio or video) is trivial:
Note the D70S shutter lag time is about 114 ms, and the lag time of the D300 is about 52 ms, which may change the Stopshot numbers when you switch cameras.