I'm looking to get some metal t-shirts and hoodies and was wondering if anyone can recommend good sites that have official, good quality shirts, reasonable shipping rates/times, etc. I've checked bandcamp because I like the fact that most of the money goes directly to the artist, but most of the stuff I'm looking for is from European bands, and I'd rather not deal with international shipping rates and time frames if possible. I also realize that many bands and their labels sell merch themselves, but as I'm looking for stuff from multiple bands I'd prefer one stop shopping if possible. I've looked around on amazon and ebay, but a lot of the reviews are iffy and I question if a lot of that stuff is authorized and/or decent quality. Thanks!

The record label sites that sell merchandise related to the bands on their label are going to be your best bet (other than the band's own site). Everything else has a chance of not being legit.

I'm re-reading some of my old comics from the 80s, and I wish there were still the 'RockShirts' vendors who sold all that stuff. I remember going into one of those stores in Gatlinburg about 20 years ago. Maybe they weren't legit then, but they seemed less shady. And a very different time as well, in terms of the content.
(I'm also reading some 70s comics, and man, I want some Sea Monkeys and XRay Glasses. And I didn't know GRIT is actually still a thing.)

Anyway, yeah, probably through the band's official sites would be the best bet.

Hot Topic?

The Hot Topic stores I've visited have a lot of more mainstream metal shirts, plenty of Metallica, Maiden, Sabbath, Ghost, etc. but not the more obscure stuff I'm looking for. But until now I never thought of checking their website and found some shirts from Bathory and Mayhem that I've never seen in their stores, so thanks for that idea.

I assume you've tried the top hits on Google when searching for metal tshirts?

If those, and the label's sites, aren't helpful, you might have luck hitting the band up on Facebook or whatever. Especially smaller bands, they generally have stock they'd be willing to sell you.