[Deus Mortis]

For both the forgeworld missile launchers and lascannons, the arms are part of these sets of 5 lads:

http://www.forgeworld.co.uk/The_Hor...rt_Squad/LEGION_MKII_HEAVY_SUPPORT_SQUAD.html

http://www.forgeworld.co.uk/The_Hor...t_Squad/LEGION_MKIII_HEAVY_SUPPORT_SQUAD.html

http://www.forgeworld.co.uk/The_Hor...rt_Squad/LEGION_MKIV_HEAVY_SUPPORT_SQUAD.html

My advice would be to either get those squads and add some chaos heads/shoulder guards/etc. But that might be too expensive for your tastes.

Or go on eBay or another bits store and buy the arms from there as well as the launchers and the 10 man regular box of CSM.

Hope that helps!