Ugh yea it can be really hard to find the right curl pattern.
The first brand I started looking at was Sensationnel, which has a pretty good range of weaves/wigs/etc in various curl patterns - it might be educational to look at their website, as they use different terminology for the curl patterns (like, some are kinky curly, some natural or body wave, etc). I think you will probably want to stay away from 'body wave' and 'deep wave' extensions because they're always looser and wavier, but it sounds like you even ordered 'spiral' extensions, so it's not your fault you got the wrong product. 'Natural wave' looks like it might be a good match for your curl pattern?
Here are some links to some Amazon extensions - I've not tried them myself, but the reviews seem pretty informative - women with 3a-3b-3c type hair saying they blended well with their natural curl pattern when they ordered the water wave for example on the first link.
A bit tighter curl pattern, Amazon
Natural wave might suit your curl pattern best
My first set of curly extensions were Kanakelon (synthetic) from the Sensationnel brand, and honestly they looked great and wore fairly well for a week or two (I glued them in back in the day!). It may not age as well as human hair, given that it gets a bit rough and tangly like synthetic Barbie hair after constant use, but I was pleasantly surprised, and it was much cheaper and avoided the 'where did my extensions come from exactly?' question that crops up often. So don't shy away from synthetic necessarily, is my advice!