Since metal frames are not allowed by Canadian Customs you'll have trouble finding them on their own. Other then Canada specific pistols, all KJW pistols are all metal, so getting a specifically KJW frame would be rather difficult. The only real way to do it would be if someone had a dead metal version pistol that you could purchase for parts. Most metal upgrade kits are designed for the brands that are always plastic, such as TM. Will a frame intended for a TM gun fit a KJW? That's hit or miss. Most guns, including KJW, are TM compatible which means the answer should be yes. But that's not always going to be the case. You could try posting in the upgrade section and see if anyone has done this, but the majority of people owning KJW pistols will have the metal versions already so I don't know how much luck you'll find.
Threaded barrels are possible, but again, whether it will fit or not is questionable. You could try KJW directly to see if they have a part like that that would fit. If not, you'll have to buy after-market and hope it will fit. With the barrel you'll have a better chance of getting something that fits then you would the frame, but it's still going to be a risk. Do some research and post in the upgrades section. Try to find someone who has done this before.