Are you looking for something like the Helix?
This year, i've reviewed a few prostate massagers:
Aneros Helix Syn
Nexus Revo Stealth
Fun Factory Stronic Zwei
Rocks Off O-Boy
The Rosa has hands down been my favourite prostate toy. It's pricey, but the orgasms it's given me has paid for it ten-fold.
The Nexus Revo is also pretty darn good too - the rotating shaft adds something new and intense, and again has led to some pretty powerful orgasms.
I guess it depends how far you want to advance - the Rosa and Revo are definitely for intermediate/advanced.
The Black Pearl is a beginners/intermediate toy - it's about the same size has the Aneros Helix but with powerful vibrations in the tip.
The Rocks Off toys are OK if you are not desperate for powerful vibrations - they are powered by the 80mm bullets, and ive found that the vibrations are weakened significantly when inside the massager, and they always left me wanting more.
the Stronic is definitely an advanced toy - it's extremely girthy for a prostate toy, and the thrusting action is actually lost a little bit once it's inserted.