Have you tried looking on this web site for some info/leads
http://www.tipsy-histories.com/
There is a lot of good Tipsy info on it and it updates the info in Raymond Cuypers book. But if you have been in regular contact with Raymond then maybe you have all of the info as he and Willem Ronge who runs this website are friends.
Or you could try the PFA BB where there might be some other Nipper builders lurking, or an advert in Popular Flying.
good luck!