I just bought a metal guard for my Mossberg 44US from Brownell's. $12 sounds like a great price, and my Mossberg guard came within a day or two via priority mail.
It was well made, fit right in, looks great, and, I'm sure, will last a lot longer than the $14-$15 plastic replacements I had seen elsewhere. No finger grooves like the original, but that didn't bother me.
Also, the order taker on the phone was a pleasure to deal with.