The springs in the bottom section are on different sides, so you need the correct side for them to install and work properly.
I would hate to be the one in an accident and got hurt because someone installed the wrong seat belt in it and it didn't function properly. The lawsuit would be pricey.
My seat belt just broke and now I'm looking for a replacement as well.
Car-Part.com--Used Auto Parts Market
is another source, but I do trust Davey and he normally has anything you need at a good price.