Hello Lynnie and KathScan.
I lost my key for my Triton T90si a while back.
This was a pain, as I live in a hard water area, meaning regular cleaning of the shower head.
I ended up using a needle nose pliers opened out to its limit, in two of the keys holes.
[broken link removed]
It required a steady hand and a bit more force than using the key, there was also the possible slip/ouch factor
However, this worked quite well until I found the key again.