I got this from the Toyotapartseast.com site. I use to go to toyotapartszone.com and order but they no longer have the images anymore...not smart on their part as I just ordered parts for my 22RE truck and used the east site since they had the photos still.

Anyhow...from a 87 camry. I think you're looking at part No. 84722 on the image, but it looks like they have a new part no. assigned to that. $52.91
84722 SWITCH, TRANSMISSION CONTROL
Replaced by:
**722-12020-C0 **722-32020-03 1 1987.10-1988.07
On my 90' I
believe it was just a screw that allowed me to lift up the shifter handle that gave me access to that O/D switch. And I
thought I remembered that there was just a spring behind that overdrive switch.....maybe just the spring is broken. It's been a while since I messed around that area (for a different reason than yours) so I can't exactly recall.