Hi orcada
welcome to the aerodrome!
Vehicles of WW I are hard to find, especially in 1/48th but have a look here
Sloppy Jalopy
and if you don't mind some scratchbuilding you can find drawings at
Welcome to Landships! - A site for WW1 Military Hardware & WW1 Military Modelling and click for Ken Musgrave plans.
And of course there are a number of cars available in 1/43rd scale and some Matchbox diecasts are fairly close to 1/48.