hey buddy your talkin about some very very very touchy TIG welding here. infact unless you do it your self you will be hard pressed to find anyone that would even do it. due to the heat distortion caused and part being so small you stand a good chance of nukin that peice!!!!!!!!
i suggest finding an A/C professional or you can always call NASA.
just get a new line made up, go to a industial supply store that make hydralic line ect. they should be able to help you custom fit a new line. it will be more cost effective. you can get a soft line made that will flex and can be made to any lenth