Adding upip to the firmware image would make developer's live much easier.
How to manually install the urllib.parse library.
Create folder /upip and add files upip.py and upip_utarfile.py manually.
Install the library with upip:
%cd /flash/upip
import upip
upip.install("micropython-urllib.parse", "/flash/lib")
To get it working, remove re.py and ffilib.py from lib. Hat-tip to Andreas.
Finally you can encode URL parameters for GET requests:
%cd /flash/lib
import urllib.parse
urllib.parse.urlencode({"a":1, "b": 2})
=> 'a=1&b=2'