Welcome to Sunline Owners Club!
This sounds like what you are talking about. This is the part that slide behind the gutter rail to create the end of the gutter. You can then clip on some of the after market extensions
RV Gutter Spouts for RV's on Sale - PPL Motor Homes
Hope this helps.
PS, Search under RV Rain Gutter Spouts and many show up. The key to searching is what they call the stuff.... A local RV dealer may even have them
Current Sunlines: 2004 T310SR, 2004 T1950, 2004 T2475, 2007 T2499, 2004 T317SR
Prior Sunlines: 2004 T2499 - Fern Blue
2005 Ford F350 Lariat, 6.8L V10 W/ 4.10 rear axle, CC, Short Bed, SRW. Reese HP trunnion bar hitch W/ HP DC
Google Custom Search For Sunline Owners Club