You can find all the bloopers from Alias at: Alias-Media. The extended version of Season 2 is there, as is Season 1, but 3 and 4 here are only previews. I don't think Alias-Media has the full DVD rips of the S3 and 4 bloopers. You'll have to find them elsewhere.
if you go on youtube.com and search alias bloopers season 1 and 4 are there. There are also some extra bloopers commentated by Kevin Weisman .aka. Marshall