Have a look here though not sure if it's right area or not. http://www.partzilla.com/parts/search/Honda/Motorcycle/2010/ST1300A+A/WATER+PIPE/parts.html
Okay - you'll certainly need to replace the broken junction (your local STealership can order a new one in - but here is the workshop manual to download for the ST1300 for you to look up how to remove/replace said part.https://dl.dropboxusercontent.com/u/53770433/ST1300-2003Manual.pdfHope this helps.
Is it a T piece, or an elbow. You should be able to find something to do the job in brass at Repco
All good. No worries will do It would be great if you two could get some pics when doing this as other Members may want to do the same retrofit.