acoustic vertical window blinds

Does anyone have  recommendations for manufacturers or suppliers of room blackening/darkening vertical window blinds for use in my mostly audio room? On each equal length side of each speaker ( a bit over 6' ) there are windows, on one side a standard double hung, on the other a rather large 4 panel bow window (over looking a fairly lovely private natural setting). I may or may not stay in this house for very long, so I neither want to overinvest nor shortchange my listening pleasure. I need to replace the current vertical blinds, and thought my fellow Audiogoner's might have some suitable suggestions.

Thanks in advance.