greenr19 - I assume you have a flat top upper with the front ramp sight, but no rear sight? That seems to be a common package being sold these days...
Yankee Hill Machine has two models that flip up and are cheaper than the price listed in your post.
Troy Industries is another company that makes custom sights - though I feel they are a bit expensive for what you are getting.
Post some pictures when you get a chance -
JD