For Halo prop makers, you have several people that create kits or finished props from the Halo universe. The best out there is Tactonyx, with his kits you actually have moving parts, but he currently makes the M6C/G, M6 SOCOM, M7 SMG, M7 SMG SOCOM, M90 Mk. II CAWS Shotgun, M392 DMR, MA5B and will soon be making the M6K. Inquire with him on pricing and further information.
NOTICE: Understand while the props have moving parts, they will not fire live rounds and you should never modify, or alter to attempt firing live rounds with the possibility of causing injury to yourself or others. Prop makers are not responsible for negative actions or injuries sustained from personal carelessness.
As for other prop makers I am not sure what they offer at this current time. If information can be provided that would come in handy. Prices are not to be listed.