Thanks for the replies,
I just ordered a Keysight U1272A. It has 30 Ohms range with a 1mOhm resolution, accuracy 0,2% +-10 digits. Of course a 4 wire measurement is much better, but it is doable.
The U1272A is also really quick and the Temperature accuracy is 1% +-1K.
BTW: There are handheld milliohmmeters with 4-wire Kelvin measurement available, but they usually don't have Temperature Type K. I use a BK Precision 880 for critical measurements, but is a LCR Meter.
Gossen Metrawatt has portables (quite expensive)
Peaktech (cheap)