Artist Derek Frost brings us this nicely done prop FBI badge that's ideal for modern scenarios. Just follow the link for the full-sized, printable version. The usual caveats regarding imitations of contemporary official paper apply.*
* Because the world is filled with idiots that think flashing a fake FBI badge is cool. The only thing worse than those idiots are the ones that excoriate you for creating or linking to prop IDs or documents because they might be "misused". Because someday some crazy man might use a fake Miskatonic University ID card for nefarious purposes.**
** I wish I was joking. After I politely pointed out that Miskatonic University isn't real they presumably followed up on their threat to report me to Homeland Security. From the lack of dark suited agents at my door I assume that resulted, at best, in a footnote being added to my file.