Let your local gunsmith replace the plunger tube. And no, you will never find another kit gun at that price. Parts are available but by the time you pay the bill, you could have bought a new 1911.
Best bet is to buy a used Springfield Armory mil spec 1911 and do a custom build. Or better yet, a Norinco 1911 if you can find one. Just make the necessary changes to suit yourself.
Both are excellent platforms for custom work.
You can buy everything you need for your project here.