The trenchcoats

What were these things exactly?

Leather trench-coats, leather dusters, oilskin dusters, etc?

A lot of terms were used. Can someone post a link of one for sale or something that was like the one they wore?

Here is a response I found on Yahoo Answers.

Question: "What kind of trench coat did Eric Harris wear?"

Answer : "It wasn't a trenchcoat, even though the media reported it as such. He and Dylan Klebold both wore long black dusters. A schoolmate of theirs got his at Sam's Club; Eric and Dylan liked the look of them and got the same coats. They were very similar to this one: [You must be registered and logged in to see this link.]

You can find other coats just like it online. Just search for "duster coats"."

Where exactly is the difference between a treanchcoat and a duster? The duster in the amazon-link looks very similar to Erics and Dylans, I agree and at this time, I realized for the first time, that their dusters looked more like a piece of clothing from a Western, than a typical goth-asseoir.

A trench coat was originally made to protect one's clothing from rain (it is a waterproof coat) and a duster was originally made to protect one's clothing from dust/dirt. So that would be correct about the duster looking like a western piece of clothing, because they were made for cowboys to wear while they were riding up and down dirt trails and shit on their horses. It kept dust and dirt off their clothes and that is why it has a slit down the back of it, so that cowboys could wear it while riding horses.