If downtime is a factor, be sure to have an entire replacement assembly (OEM, or of any flavor) on hand before grabbing a wrench. When the FFM leaks, it's usually fatal, either failed potting or housing crack. Time-wise, an OEM replacement would be the quickest and simplest, having no consideration for accommodating a foreign agent into the system. If your leaking FFM is original, praise its quality for lasting this long. Its 30th birthday is mere months away.