I like Naut support but if hooking people for instakills isn't an option / makes you lose trades you are USELESS in lane for a while, though he's almost always relevant lanegame as an awesome tank/disruptor. Unfortunately if your team gives up before you get there it's not horrendously helpful ><
Thresh is great, I've been playing a lot of him lately. Once you really get the hang of relic shield hitting and how and when to bully, he's extremely versatile. I would recommend playing a LOT of games on him before taking him to ranked, though. He's a great off-tank that does ok damage. He's NOT good as the only tank on the team, though! He has a heck of a lot of CC (though it's not instantaneous, making him a little weak to assassins) and his lantern can save a bad play or make a good one! (Unfortunately also tends to be ignored in lower elos, once you get to low gold, people get the hint sometimes...)
I want to recommend Braum, I used to play more of him last season. He just doesn't feel as useful as he used to. His passive is nice but if you can't land Qs / get to the enemy all you can really do is block a skillshot / auto every like 15 seconds lol. He's pretty good in teamfights cuz you can lock down that target that needs to be / disrupt / slow, but I feel Naut can really do it better.
Leona is hecka fun and very good in low elo as people have a hard time understanding how to counter her. I think she loses effectiveness as you go up, though, unless you're very good at her. She's more geared for engaging so Leona players tend to ignore their carries / not peel, if you can do that you're probably gonna do a little better lol. She can be strong in the right hands, and her ult can be game-changing if your team follows up.
Also Taric is a good mix of caster supp with tank supp, he has healing and shielding tools with his really OP ult. If you can get your entire team in your ult, it can completely change the outcome of a teamfight all on your own. Having a stun gives you some choice over who to focus and you can protect important teammates with your shield/heal all at the same time. If you want a carry supp, I think Taric is up there right now.
I think Taric is your best bet, but otherwise: in Bronze - Silver Naut and Leona? And once you start getting towards gold perhaps you can throw Thresh in there?
I'm also gonna add a footnote here for Janna. I know she doesn't strike you immediately as "tank support" but she has a LOT of carry potential (and is deceptively tanky). I like running full tank runes on her so she's pretty much a tank. Her shields basically make anyone that needs it much tankier, and you can buff them with Chalice heals or Locket shields or Mikaels heal and it makes it very, very hard to kill anybody. She basically makes anyone you need a tank! And can clutch save one person or a whole team with that healing ult. Also people tend to ignore you so you can just run rampant lol.
Her only real downside is if your adc is actually 100% terrible and the enemy is a poke lane you are gonna have a hard / very boring time. Course that's probably true for anybody lol.
Sorry if this is like way overkill on the info depart lmao. Disclaimer this is all my opinion / things I've noticed and I'm technically only a Silver in my promos, RIP.