Resume broken Firefox download (.part) on Mac?

Was downloading a large file in Firefox and lost my internet connection about 500MB's in (yes, should have been using a download manager but hindsight is a great thing).

I still have the 500MB .part file but can't find a way to resume people.

I've read Flashget and Getright will both do but neither are supported on Mac.

Any suggestions?

Thanks in advance.