WarpMyMind

Is there file that will make my bladder smaller then it is

There should be. Don't recall what it was.

http://www.warpmymind.com/Files/7146/The-Shrinking-Bladder.php

Any file that encourages you to wet freely will have that effect over time. For that matter, you don't even need a file. If you keep your muscles relaxed and just let your urine flow whenever it feels like it (i.e. never hold it), your bladder will naturally shrink, as it no longer is stretched out by getting full.