I recently saw a link to a webpage where a guy recommended using a MityVac. That's a small, handheld pump, originally sold to use the vacuum (less preferrable than the better positive pressure) method to flush brake fluid.

The guy said that the MityVac can be used to go either way, pumping out old fluid and pumping in the new fluid. Just use graduated containers to be sure that you've got the right volume.

I don't know if this is what you were thinking of, but it's a possibility -- although I'm not endorsing it, as I haven't used the MityVac for this.

In boating shops, there are electrically powered pumps for doing oil changes in marine (inboard) engines -- but that might be overkill, as the reliable ones are in the $100-200 range, and you want to transfer barely a liter of fluid.

Good luck.