First, we need to know exactly what you want us to look for. Are the gauntlet and flaming sword on a shield (in which case, it is a "coat of arms"), or are they placed on a wreath (a "torse") above the shield, perhaps atop a helmet (in which case, it is a "crest")? Which of these it is supposed to be will help determine where are the best places to look.
All that said, a gauntlet holding a sword (flaming or not) sounds more like a crest than it does a coat of arms, in which case the first place to look would be a book called Fairbairn's "Crests".
Looking in Fairbairn, there are number of different crests listed for various Fleming families. Most are goat's heads, but one, "Fleming, Eng. and Wel.," has "A hand gauntleted holding a sword proper." See the attached .jpg ("Proper" means that the gauntlet is colored silver or white, and the sword has a gold hilt and quillons and a silver blade.)
I did not find any crests in Fairbairn where the sword was flaming.
I hope that this information is helpful.