Basic blender went bad (motor ran but spindle wasn’t rotating). I wanted to disassemble to see if it could be repaired. Three of the four screws were Phillips head. I had to cut the casing open in order to discover why I couldn’t unscrew the fourth. It was a slotted spanner.
Thought they might sell these specialty tools online, but 3 minutes of searching came up with nothing. Might be time to get creative.
Do you have the room to get a Dremel in there the cut it so a regular flathead will work?
If not, maybe try to use needle noise pliers as your screwdriver.
As a last resort, pick up a cheap screwdriver and cut it to make it slotted.
Edit: I love how quickly several people have commented with links to the needed tools. Thanks to all of you!
https://www.amazon.com/ORIA-Precision-Screwdriver-Extension-Smartphone/dp/B01E16J6RQ?source=ps-sl-shoppingads-lpcontext&ref_=fplfs&psc=1&smid=A2FOADTO08BQD0&th=1#immersive-view_1715788586172
I have this exact set. The bit he needs is second from the right, third from the bottom
Depending on the size, I’ve absolutely gotten small versions of these bits in IT/Electronics repair kits.