Happened to me on the motorway earlier this year - was able to turn off, find a Motor spares shop and amazingly they had a wing mirror glass to replace the one lost - about £10 later I was back on my way!
The glass was attached using a piece of double sided tape - the pad was already attached to the glass and after being peeled back the glass amd attached pad was carefully attached in the right place using the cardboard packaging as a spacer at the bottom - the packaging recommended doing this when the sticky pad was warm.
You might ask at a Motor Factors if they had any appropriate double sided pads / tape?