The remote release works by IR. Works great. Yes, the D-50 has the
capability.

There is nothing for the D50 (at least not mechanical).

http://search.ebay.ca/_W0QQsassZbearislandtcQQhtZ-1

has an interesting solution though if you really need a "wired" solution
(WiRed IR Remote)

You want the ML-L3 Remote Control Transmitter.

http://www.nikonusa.com/template.php?cat=1&grp=56&productNr=4730

It is not a "cable release" but it performs the same basic function and it
causes even less camera movement than a cable release. They cost about $17.
It only works with the D40, D50, D70, D70s N65 and N75 cameras. Beyond that,
there are not many options for the D50.

The D80 and up have various other cable and wireless release options, but
none of them are as simple to use or as convenient as the ML-L3. The ML-3
Compact Modulite Remote Control Set, for example, has a big remote controller
and an infrared receiver which occupies the camera's flash shoe and connects
to the front of the camera with cable. Not cool. Granted, it does a few more
things (like trip the shutter when something moves between the remote and the
receiver), but you more than pay for it in price, weight, bulk, and plenty of
fiddling around to get it to work right.