I main supp Taric and I love him when played correctly taric is one of the best supports but it occurred to me I have no other supps in my arsenal and was wondering who would be a good backup I was considering nami or alistair but not sure.
Alistar, Tahm, Thresh, all pretty nice picks. Tahm is wonderfully broken right now.
is insanely broken but i find him boring to play.
is my fav support right now.
can't go wrong with 
though.
If you like Taric's playstyle of a tanky support with a good balance between offense and defense, I'd highly recommend Braum who has a similar play pattern and goal as Taric, but with more room to make plays and a higher skillcap.
Thresh is a staple (... says the support main who doesn't play him on principle, but whatever XD) well-rounded support that fits most comps, most match-ups and most situations, good offensively and defensively as well, if you are good with skillshots.
Shen could also be a good option, tanky, has the taunt to engage or peel, and the ult for amazing offensive and defensive plays (but require good coordination to be used offensively).
Alistar is a good option as well, however if you don't have very nice ping, I'd be careful about maining him because the timing on his combo is hard to get off on suboptimal ping. I also think he's not that "well rounded" as I find his lane weak to poke and his engage is telegraphed without burning flash; personally I was never a huge fan of Alistar, but I know a lot of people enjoy him.
If you're in for a squishier champion, Nami is also a good all around pick that I would consider. She has the ability to poke, sustain, buff, engage and disengage nicely.
Tahm is stupidly broken, is probably going to get nerfed, and has a high ban rate atm, I wouldn't bother going for him unless you don't draft much.
In my eyes your options 
> > 
> > 
> (in terms of how I think they'd fit you, not in terms of champion strength).
has such high utility with a perma-slow to enemies or speed boost to allies. Has a stun and great zoning with time bombs. Slap your ult on your adc and they can turret dive for a double and speed boost them out of turrets harm after they re spawn. The AoE damage is great in team fights and after laning phase you deal surprisingly high damage. Build a little CDR and his ult is up practically every team fight, and bringing one person back to full health can really change the whole fight.
is the definition of a lock-down support. His passive allows his autos to be a mini- stun. between that, his knock up ult, his pull, and his AoE slow you can't escape him. Plus he is tanky enough with his shield to be a bullet sponge. Requires very little champion knowledge to do well.
Underestimated. Very very underestimated. His W heals when he is hit with auto attacks, so the enemy adc will just heal you if you max this first. Q is a high damage slow, and e is a speed buff to your own ADC so they never too far behind. use your W for shield and pop his ult to heal yourself and lock-down opponents while your ADC blasts them down. You choose when to come out of ult so you can secure kills or lock-down as long as possible. get a spirit visage and you're good to go
I feel that could also be a champion that you might like. You said you wanted someone who is well rounded and Thresh is just that. His q and e combo makes a great engage while lantern and the box make great escapes or disengages. You can zone people easily with Thresh and early levels your autos really do damage with the e passive.
You might also like , he is like taric because he has a point and click knockup that acts like taric's q. He is naturally tanky and gets a decent sized shield late game with w. His autos root each person for about a second and then it makes it easy to poke with e.
If you are used to someone who is melee and you want another straight tank you could go for naut but if you want someone who is ranged but deals the same damage as a melee support pick thresh. There is only one equivalent to thresh in terms of saving his team and that one time is tahm kench's w.
