I have a book on DIY which show's you many different field's of DIY, but in particular plumbing, it show's you how to replace burst pipe's and mend leak's, it shouldn't be too hard to find at your nearest library it's called STEP BY STEP DIY, but I'm sure any book on DIY Plumbing will be helpful in solving your problem. You could replace the pipe yourself, the book I told you about give's you step by step instruction's for replacing pipes etc. Hope my answer has helped, GOOD LUCK.

Shdy,

Please see the image below and tell us where is your leak, if the leak is at the other end of the supply line connected to the toilet you may need to tighten the nut or replace the gasket, Thanks.

John

Good pics from John but I am guessing your leak is up under the tank. Does it start getting wet right below the tank where the line enters the tank? This fitting is most likely plastic and designed to be hand tight, you can snug it a quarter turn more with a channel lock. Just let us know if this is your situation