Neil
For some reason the topic you posted does not accept replies and it does not appear to be locked.
I wrote an email to Seiko asking what they considered a replacement for the now obsolete SQ100/70.
I was advised that the Seiko SQ200 was the nearest model.
Seiko SQ 200
At the bottom right corner of the webpage there's links for:
1. Sound Samples
2. Specifications
3. User Manual Pdf
I don't know what volume it produces but there is a volume control.
Dermot