I posted a pile of HotSawz presets here a few years back.  I doubt that I targeted a GR300 in there, but it’ll be something else to play around with.  Seems to me that all/most of the tools are there in HotSawz for a reasonable emulation.  It may take some wizardry to capture that GR300 quirky design & nuance.

https://www.eventideaudio.com/community/forum/stompboxes/broken-sawtooth-66-hotsawz-presets