Kanger aerotank and Aspire Nautilus are two of the more popular clearmizers around at the moment. Both have adjustable airflow and decent sized capacities.
They also both use dual coil coil heads in them so they do produce significantly more flavor and vapor than most others, although because of this, for best results I'd recommend them for variable voltage devices (some have reported that they work fine on non VV devices, but I am just speaking in general terms and for best results)
They are both 510 threaded.
When I use a topper, I use a kayfun but my friend has an Aspire clearo. I tried it recently and I was very surprised at the great flavor and vapor it produced.
For some good reviews on different clearomizers, I'd recommend PBusardo's channel on youtube.