Hello Evan,
I own some Green Mountain longbows including two Stingrays ("regular" & flatbow versions), they are fine longbows. A few years ago I would have steered you towards a JD Berry Taipan as it was a very similar design to the Stingray (rounded forward-handled risers with the majority of the limb laminations on the belly of the riser & mild R/D design). They are no longer made but it would be another option to pick up used.
Northern Mist Longbows currently builds a model that is quite similar to the GM Stingray that they call the Whisper. It is not a R/D design however. I own a 62" Whisper with a locator grip and it is also a fine longbow.
There may be other options out there, these are just two that I know of.
I hope this helps a bit.
Take Care,
Tom