seems like levi's is constantly tinkering with the 501. look on the inside tag where it says "made in..." and also look at the backside of the top button and note the number. that number denotes the specific factory from where they come from.
nowadays they make em in mexico, egypt mostly, but i've seen haiti... etc etc.
the different factories make em slightly different. best advice i can offer is go to kohl's or wherever they sell 501s rinsed and try to match that information from the ones that you really like. if you do find them again i would also consider buying multiple pairs (i don't work for levi's lol) if you like em that much so that when you blow your current pairs you have more.
when i was in college we had an old leather guy who sold handmade leather sandals and if i was thinking clearly i would've bought have a dozen. what costs me $30 back then is next to impossible to find and incredibly expensive to order special.