Hi, orrin.
To the best of my knowledge, there aren't any GIMP SFS's for the relatively new 64-bit Pups. However.....
I take it you're after an SFS so you can load/unload as and when you want, yes? I'm guessing you essentially want something self-contained?
Have you heard of AppImages? They're self-contained progs/apps which will run from any OS, anywhere, as and when you want. Rather like the Windows 'PortableApps', you can run them from a USB stick if you want, and transfer them between Pups.
http://appimage.org/
Below is a link to a webpage where you can download the 64-bit AppImage for GIMP 2.9 (the developer version). I've tried this in both Tahr64 and Slacko64 6.3.0 (the predecessor to yours.) It runs without issue.
https://bintray.com/probono/AppImages/G ... 2.15#files
This is in the 'official' repo linked to from the AppImage site. The first line in the list is the download you want.
**GIMP-2.9.3.glibc2.15-x86_64.AppImage**
When you've downloaded it, you'll need to right-click on the AppImage and choose 'Properties'. Tick the three 'Exec' checkboxes on the right-hand side, then hit 'Refresh'. This'll make it executable.
Then, just left-click on it as you would for anything else, to start it. Be patient; these things can take a wee while to start the first time, because it's setting up ~/.cache and ~/.config files in /root, the same as any other application would.
If you decide to try this, let me know if it works for you, please.
Mike.