This is an older model, which I haven't shown on the blog before. I mentioned a while ago the Chapterhouse Studios conversion beamer kit, and this model shows it off very well.
Sadly, I don't think that this kit is being cast any longer.
The kit originally came with two backpack choices, as well as the beamer and a servo-arm. One backpack allows you to use both of these, whilst the other allows you to use either the beamer or an arm.
This is also one of my favourite Techmarine models - I really like the helmet and additional bionic detailing. The armour appears a bit more ornate than some of the other GW Techmarines, and so I thought this piece would be ideal as a Grey Knights Techmarine.
For reference, the only other (official) conversion beamers currently in production are that for the Comptemptor Dreadnought (too big for a Marine) and Valthex of the Astral Claws (available from FW). The latter is a really nice model, and I'm going to be picking one up for conversion work in the next few months.