My library has a lendable "Ultimate Screwdriver Kit" that has every bit size and type I've ever heard of, security Torx, pentalobe, oval, gamebit, spanner, etc etc. Also a bunch of different styles of bit holder, and a bunch of attachments like angle adapters, depth setters, torque limiters, etc. Only tangentially relevant I guess... but if you run into a problem like this again, check your local library to potentially avoid having to buy obscure bits online!

I mean a blender isn't exactly the worst things to have security bits on.

Looks like a job for a regular flathead and a grinding wheel.

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!

Oh, I have that bit. Its not even the weirdest

Were you able to fix it?

I know I have terrible eyesight, but it seems like I opened blind or dyslexic community. Why only few people noticed

I had to cut the casing open in order to discover why I couldn't unscrew the fourth.