Did any of you actually READ what the OP wants?
SMALLER THAN AN EGO-V V2!
If you are offering something larger than that then you are NOT paying attention.
Now, to the OP....
Have you looked at a Lavatube Mini?
Second from the left.
As you can see it's shorter than a 900 mAh eGo, is VV and is large and solid enough to take big tanks as well as small ones. It doesn't have passthrough charging but it does have replacable batteries so you can charge one while using another.
SMALLER THAN AN EGO-V V2!

If you are offering something larger than that then you are NOT paying attention.
Now, to the OP....
Have you looked at a Lavatube Mini?

Second from the left.
As you can see it's shorter than a 900 mAh eGo, is VV and is large and solid enough to take big tanks as well as small ones. It doesn't have passthrough charging but it does have replacable batteries so you can charge one while using another.