I do not think there is any way at the moment. Larger cursor (and in one case smaller) has been requested from the Gimp devs in the past
From a couple of years ago: https://gitlab.gnome.org/GNOME/gimp/-/issues/5513 and still considered.
...so they are looking at it (even with a magnifying glass) It might come in with Gimp 3.0
From that bug report this one: https://gitlab.gnome.org/GNOME/gimp/-/issues/8768
Send another bug report as a reminder.
From a couple of years ago: https://gitlab.gnome.org/GNOME/gimp/-/issues/5513 and still considered.
...so they are looking at it (even with a magnifying glass) It might come in with Gimp 3.0
From that bug report this one: https://gitlab.gnome.org/GNOME/gimp/-/issues/8768
Send another bug report as a reminder.