I'm sort of trying to make a custom one up from a short section of 3" Stainless exhaust tubing. Cap the ends, weld on some bungs for the inlet/outlet lines, add a drain hole and fill with steel scourers. Should only work out to about $50-60.
They are worth it noss, oil in your fuel/air mix drops the octane rating of your fuel. (don't ask me how much, can be as little as a point, could be as much as 5 points.)