I bought a small 40mm 12V noctua fan for my T4 and the connector which fits the board.
But it came without pins.
So, I took a more drastic approach and soldered the fan directly to the power supply (see picture) and installed the fan with some tie wraps.
=> downside: always on. (very small noise)
Temperatures:
- WITHOUT FAN:
# IDLE: +- 50 °C
# 100% usage (dd | gzip): +-80 °C
- WITH FAN:
# IDLE: 28°C
# 100% usage (dd | gzip): +-50°C