If you own a 2011 tv from Sony, Panasonic and Samsung (i think it's just these three) then an agreement was made last year to make glasses that work across all these brands and the first wave of these will arrive this year. You can then take your glasses round a friends for example and they will work as long as the tv in question is made by one of these manufacturers, the new glasses will work with any 2011 3D tv onwards but i've not seen anymore details since the initiative was announced last year.
As for 3rd party glasses there aren't many pairs out there that i have seen but i would be doubtful that they would be very good, i can't find any reviews either which just rings alarm bells. If they are cheap enough they may be worth a try, perhaps just get one pair to start, but if it was me i would stick with the glasses that were made for the tv despite the extra cost.