Finding something in between the Reaper Eldritch Demon & the Bones Cthulhu other than those already mentioned is a bit tricky. The Bones model should be cheap, but if it's too big (7" +) I'd go for the aforementioned Scibor one - unfortunately it's probably more expensive than the Bones one, particularly importing it to the US. The Khurasan one is good (is his site back up again?) & being US based won't demand your first born in carriage charges.
If you can wait a little while, Dust are releasing a 'Cultist' faction with two 'Cthulhu' sculpts, one flying & one with some scenery (they're supposed to be available by Christmas but who knows with them...). They seem to be the size you want & shouldn't be too pricy.