I don't think there is anything out there which is that cheap. Probably your best bet is to get three matching "center channel" speakers and line them up. The other problem you has is that your width is limited to about 43". Most center channels are at least 20-21" which would require about 63" width.
You could try to find something small, such as Cambridge Audio SX-70 center channel speaker, which is 14-1/4" wide (three would require 43" exactly). They are $180 each from Crutchfield.
There's only one truly passive soundbar that I know of. Legacy Audio has a "Soundbar" passive speaker, but it's 48" wide and going to cost around $1300-1400.
You could try to find something small, such as Cambridge Audio SX-70 center channel speaker, which is 14-1/4" wide (three would require 43" exactly). They are $180 each from Crutchfield.
There's only one truly passive soundbar that I know of. Legacy Audio has a "Soundbar" passive speaker, but it's 48" wide and going to cost around $1300-1400.