The mounted Halfling Barbarian / Druid question

[Thomas Elfing Johansen]

I hope you guys can help me.

I would like to play a mounted multiclass halfling Barbarian/Druid, and would like my Druid animal companion to keep advancing when I'm taking levels as a Barbarian. Is there anyway I can make this happen?
In the good old 3.5 there was feat called Natural Bond (Complete adventures):
Add three to your Effective Druid level (not to exceed your Character level) for determining your Animal Companion’s bonuses. If you have more than one Animal Companion, this feat applies to only one.

Hope you can help me

[RuyanVe]

Greetings, fellow traveller.

There is a feat called Boon Companion: Click.

This seems to do the trick but only for 4 levels of non-druid/ranger levels.

Ruyan.