Replacing Vacuum tubing 1.9 DTI and best place to get it?

Hi does anyone know what lengths and also diameter of vacuum tubing id need to replace the stock fabric covered tubing in an 2000 octavia 1.9 TDI, as i think my sons car has a vacuum leak somehwere and these old wore out tubes seem like the logical place to start replacements,

It would be great if anyone has links to products

also can anyone provide me with a diagram of the intercooler pipework and the most common place a vacuum leak could be there (as someone told my son the most likely place is behind the intercooler) and i dont know whether he meant the inter cooler or some vacuum pipes around it