Can anyone recommend a good, inexpensive beer stopper, to save an unfinished bottle?

I was thinking of getting some bottle stoppers for myself and my friends for giftmas. There have been too many occasions where we've have had to chug, or pour out, half of some delicious beer that we can't finish for one reason or another.

After searching for a bit, it seems that there are very few stoppers made for beer, besides these which have less than stellar reviews.

I'd like to find a lever stopper like this or this but they all say that they're for wine or champagne, and I have no idea if they work for beer (the reviews/descriptions don't ever say).

So... any suggestions/advice?