F-115 2005 injector unit part number is 68V-8A360-00-00, runs about $125 - 150 US new, or $60 to $100 remanufactured (at least in the US); part number is likely the same for other years, but you should check to be sure (go to http://yamahamc.partsandwarranty.com/SyndicateNav.cfm and select your year/motor.)
From there you should be able to search suppliers that have them.
