you're might be looking for a "stay extender" here are some quick examples i've googled:
Johnson Marine: Stay Extenders w/Pins: Mauri Pro Sailing
Hayn makes one too, but the url keeps getting corrupted, do a google search.
Or give Rigging Only
a call, they are awsome to work with and give a great price. There may be a threaded extender that I'm not aware of.