B&H is usually a safe choice. Newegg and Amazon can be too if you're careful with who the seller is. Drives for work often get placed through an enterprise wholesaler like CDW or MARKIT.

For my personal NAS projects, I generally buy a WD MyBook/EasyStore from Best Buy and shuck the drive. The drive on the inside is generally a WD White Label, which is a WD Red (NAS drive) that didn't meet QA specs. I wouldn't rely on them for mission critical stuff, but they're perfect for a Plex server and you can generally get them cheap. (worth noting that I've seen a few say they've been removing the SATA connections from these recently and I haven't bought one in about 15 months so do some research before purchasing)

I just went through this so I can well you B&H and Microcenter both did well for me. I actually had a failed drive from B&H (one of two) who took care of it and refunded my money. The best advice I can give though it order drives from different suppliers or batches so you don't get two from the same batch which can sometimes have a problem.