Adafruit #1501 (5V), and #1500 (3.3V).
Note that if you want to drive Neopixel LEDs with a Trinket, you must use the 5V version. Driving NeoPixel LEDs with a 3.3V Trinket is completely unreliable. The NeoPixels really need 4.5 to 5V signals to function. The 3.3V signals will sometimes work, just enough to be very confusing.
Programming a Trinket:
Remove external power from the Trinket.
Disconnect pins #3 and #4, which are used for the USB communications, as well as for general purpose Input/Output.
Tools, Programmer, USBtinyISP
Tools, Board, Adafruit Trinket 8MHz
Tools, Port, no selection needed. Very confusing, but really, you don’t need to select anything.
Press and release the Trinket reset button. Red LED should flash for 10 seconds. Programming must start during that 10 seconds.
By the way,
#0 runs the red LED. #1 and #0 can be used for pseudo-analog PWM output by calling for an analogWrite command.