maskigirl,
As I understand it, the broker who you've contracted with is unavailable or unwilling to pay this invoice. Logically, the manufacturer who contracted with the broker would have a greater degree of influence over the broker than either you or the consignee. The response the manufacturer gave you when looking for payment indicates that they do not care whether you ever collect this or not. If they had indicated that that would try to intercede with the broker on your behalf, I would then follow the measured collection methods recommended by Freight Broker. However, since you said that this is now months old, and considering the response from the manufacturer, then I wouldn't hesitate to claim directly from the consignee. It may seem unfair if eventually the manufacturer has to pay twice, but that is the cost to them for their lack of due diligence when contracting with a disreputable broker.
You can sue the consignee (beneficial party), in small claims court and cite the Mercantile Act - there's plenty of jurisprudence available to substantiate and reinforce your claim and in my opinion, the manufacturer would be irresponsible to ignore this matter.