I'm glad that you asked and I hope that your T will find a spot for you this week.
I also thought that I could ask for an extra session only in emergencies and as there is never the emergency for me... But sometimes I was writing e-mails after sessions to get rid of some thoughts or if something was bothering me, and in one e-mail I wrote something that on one hand I thought that it would be great to have an additional session that week but... And I got pretty soon a response that actually there was a spot free and I could take it if I wanted... And for sure I was not in a crisis then and it worked pretty well and helped a lot, so now I think that you don't have to be in a crisis to ask for an additional session

Good luck