The P30 match weight is for sale on the webstore. The weight is sized to fit a P30L extended barrel in the P30 slide perfectly. There are a couple options on barrels. Here are the most popular.
Barrels from EFK Firedragon
P30L Extended Ported barrel: This is an ideal solution. Already ported, comes in black or stainless, minimal waiting. The ports are not as directional as the weight, so you will burn the sides of the weight, but that isn't anything major.
P30L Extended Threaded barrel (with no threads cut in it, special order call EFK and ask for it.): Perfect solution, but lead time is an issue. I had my barrel ported by MagnaPort to get something that was ported only along the top. Does not burn the weight, but less porting than the EFK Ported barrel so the muzzle flip reduction is slightly lower.
P30 Threaded Barrel: This will work, but the looks of it may not be what you are wanting. The barrel will not reach the end of the weight.
P30L Threaded Barrel: This also will work, but the looks of it may not be what you are wanting. The barrel will not reach the end of the weight.
Barrels from Jarvis (the Jarvis barrels are only available in 9MM, I shoot 40S&W so they are untested by me.)
P30L Extended Ported Barrel
P30 Threaded Barrel
P30L Threaded Barrel
Please don't use the Standard length barrel. Flames get directed back into the the weight and may burn the frame of your pistol as well as your knuckles. Plus the blast puts a huge strain on the metal, it may break under sustained fire.