there are lots of companies providing those services, depending on your budget:
(no particular order):
Jeppesen
Univeresal
Skyplan
UAS
Hadid
ASM
Jetex Flight Support
Palm Aviation
RAK Aviation
you can search them on the web, they provide computerised FPL, fuelling, handling, overfly permits, nav fees and quotes. You can either arrange cash or pre-payment prior to your flight.