9x18 Makarov threaded barrel.

[Grapeshot]

Are there any suppliers out there that offer a barrel dismounting/remounting tool and a longer barrel with a threaded muzzle for the Makarov pistol?

[subsonic]

Yes. You'll have to google it though. I don't remember where i saw them.

They also make .380 barrels.

[HATCH]

Federal Arms made them but they are out of business.

Here is a 380 one -> http://www.gunbroker.com/Auction/ViewItem.aspx?Item=245882024

[Artful]

Most of the Federal barrel's sold thru Markov.com were 1/2x32 - most can's are 1/2x28
Adco or Tornado tech can extend your existing barrel. But as a blowback it will be noisy - best best is 380 barrel with strong spring.
Your best bet for a barrel removal tool will be one of auctions or make it yourself.