I haven't seen one for a small diameter pipe, but what you're looking for is some type of drain flange:

The top is wider to hold it in the opening, the rubber washer is below to seal the connection, and then you use a metal washer and a nut to tighten it to the surface.
With a small diameter pipe, you can improvise this with a threaded pipe and a second nut (pardon the ascii art, this is a cross section view):
| |
nut ===| |===
rubber washer ....| |....
surface --------------| |--------------
metal washer ....| |....
nut ===| |===
|drain|
| |
The downside of the improvised version is the nut and threaded pipe will sit up a bit from the bottom, so this doesn't work as well if you need it to drain completely to the bottom.