Help, upgrades to my vfc scar ?

VeiledSovereign I bought a vfc scar mk17 awhile ago and did some mods to it since then; a tight bore barrel, higher power motor, high charge battery, fixing the crappy wiring, high power spring and a adjustable fps piston (but i havent installed it yet). over all my scar is at what i wanted it to be except for two kinda not so small things.
One is to have the standard short outer barrel extended to a longer spec looking barrel, only thing is i cant find where to buy one, i only found two websites that sell it but its been out of stock for awhile i think. If you know where i can find one that would be great. Here the website where they have them but its not in stock.
www.wgcshop.com/wgc2008/main/product_detail1.php%20barrel&catid=&cat=

Second thing i want to do is to possibly change the lower receiver from the bulky and expensive mk17 H to the mk16 L m4 style mags. This would help me with adding more clips to my rig without taking up so much space and also its a hell of a lot cheaper. I asked a few people in person, they werent sure and i cant find anything about it online about switching the lower receivers. Is it compatible with the mk17 gear box and etc ? I know i should have just bought the mk16 but i didnt realize it till after and for some reason i stuck to it until now and its a bit too late to just sell the gun with a lot of new stuff in it. If you know anything about this or the outer barrel, please comment i could really use any help possible. Heres a link to the lower receiver.
www.wgcshop.com/wgc2008/main/product_detail1.php%20Parts%20for%20AEG&catid=71&cat=414

11 months ago