I have these. They say G2, not G2si, but they are round. Silver face. Very lightly tested and in great shape. Let me know if these might work.
Thanks for your interest.
I have just checked datasheet of these tweeters G2, G2i and G2si.
The G2i and the G2si is very similar and interchangable, but the G2. The G2 seems to got higher impedance and heavier ribbon.
G2: Aurum cantus
G2i/G2si: Aurum cantus