Choices of parts for outboards isn't quite as varied as for cars/trucks. There isn't a huge aftermarket. Your choices will likely be OEM or Sierra. You should be able to find them here at iboats http://www.iboats.com/115-E115TSXEUA/dm/view_id.1554934
Edit: Looking at the parts list, it looks like the wires are integral to the power pack.
What is the reason for replacing the wires ?---What is the motor doing / not doing ?----Sparkplug wires are not part of the powerpack !-----Look for item 29 / 30 / 31