Numrich has a few parts for your rifle...
http://www.gunpartscorp.com/catalog/...px?catid=10222

And here is something from Armscor that has all the part numbers and a picture of the rifle broken down so I am guessing they have parts available to order...
http://www.armscor.com.ph/img/pdf/MAK22.pdf

and a link to some 15rd mags. I havent seen any higher capacity but havent looked in some time...
http://www.advancedtactical.com/inde...hk=1&Itemid=53

as for price I have seen them usually from $150-250...