you will have to forgive the fact that i dont know the part names
here you see 5 pics:
http://www.gp-web.com/en/productspop.php?pid=1816
the top one has a reciever assembly, 3 pins and a strap point.
1. what your interested in is the 2 large RINGS, these parts are what you need.
2. the 3rd pic shows side angle of the barrel, above the barrel running the length of it, is a small metal rod. you also need this!!
3. from the pics your gun looks like it takes this type of hand gaurd:
http://www.fire-support.co.uk/product/gp-m4-handguard
also in this item from fire support comes one of those RINGS!!! you only need the other one which im afraid is notoriously hard to find, here is a breakdown pic of the part, courtesy of fire support again
http://www.fire-support.co.uk/product/clas...-m4-ris-wbarrel
sorry i cant help anymore, i have no time to do any research, nutster will probs know where to get these things from. but if not i would speak to chris from REDWOLF, (just google redwolf, then eamil the UK site) he has literally warehouses full of parts m8
cheers.....