There is a link to the citysearch list of consignment and thrift stores. There are only six stores listed, so it's not that great, but it is a start. http://austin.citysearch.com/roundup/36961?cslink=search_edroundup_1_1
Roundup of vintage stores, sorted by area of town.
Vintage stores tend to have things that are in better condition, so therefore is sometimes more expensive. This isn't always the case, but don't be shocked if it happens.
Other places to try:
Salvation Army (If you don't mind giving money to hateful fuckwads who are homophobic)
If somewhere is far and you don't own a car, plan a group trip so several people can look for stuff.
For a Riff coat:
Call tux shops and see if they're getting rid of any. If it's damaged, big deal. Most of the time they'll sell used ones for $80.
Personal Columbia hats:
I think that the top hats are $15 or so at the Bazar.
If you know anyone that's going to DisneyLand/World send them with some cash to get you Mickey ears. Specify Mickey, not Minnie, and get them personalized with Columbia instead of your name. Hell, get them personalized with Cocksucker, it doesn't matter. You have your own fuckin' ears.