I'd rate the Kestrel 4000 handheld AWS. I've had one for almost 2
years, it's been with me to more countries than I can remember, it's
handled Finland in December and Texas in June, and I used it to log
T/RH/PPP/ff avg/ff gust at 1 min intervals during the annular eclipse
in Madrid on 3 October last.

It's about the size and weight of a mobile phone, has all the major
elements except rainfall and wind direction (... obviously!), logs the
past 400 observations at intervals from 2 sec to 5 hr, runs for a year
off 2 AAA batteries, and is astonishingly accurate - I've left it
logging alongside my much more expensive sensors in my Stevenson Screen
for several days, and you'd be hard pushed to tell the difference. A
bit pricey (about £280 as I recall, more for the PC interface to
download the observations) but worth its weight in platinum. This is
one piece of kit I take on every business trip. (Oh, by the way, I
don't have any shares in the manufacturers ... but I wish I had!)

I bought mine from meteorologica.co.uk, but there's quite a few places
sell it and you can shop around for the best deal.

Regards -- Stephen