Gillie, I have never seen a set up for thru hull scuppers..here is a discussion that I found regarding converting from thru hulls to thru transom. I might do this variation/modification in future as well. I have never been bold enough or have gone out enough times yet to pull my thru hull plugs.
http://www.classicseacraft.com/forum...r=62803&Forum=,,,All_Forums,,,&Words=scuppers&Searchpage=3&Limit =25&Main=62729&Search=true&where=bodysub&Name=&dat erange=1&newerval=4&newertype=y&olderval=&oldertyp e=&bodyprev=#Post62803
Also I know there are 45/90 degree ball scuppers (used mainly for below waterline)that you can mount in the deck hole (after modification) after removing your original thru hull pipe, then run hose/pipe to rear and hook up to thru transom fitting. here is one example..did quick google search to give you an idea or another alternative.
http://www.thmarine.com/product.cfm?PRID=56
-Fred