I have some single flute tiny endmills specialised for cutting plastics in high RPM small spindles (like engraving spindles).
I have single flute endmills in 1mm and 2mm diameter, these won't take a lot of torque to spin and they are excellent for cutting plastics. They have 1/8" shank.
I can't remember the supplier but it was a US firm that have a massive range of bits.
You might also find a drop of water or water with a tiny amount of detergent will help a lot too both to keep the tool and material cool and lube it to throw off chips.