I've got an aluminium racing jack from Hare and Forbes.
J042 | Alloy - Low Profile Hydraulic Garage Jack | machineryhouse.com.au
I like it a lot. It's light weight and easy to pick up and move around. It's got a 2 stage pump so it goes up quickly till it encounters enough weight then the 2nd stage hydraulics kick in and it's easy to pump.
It's been low enough to get under my chassis OK. The issue often is with any jack like this is not how low it is at the front but how low it is at the back. Once you have slid it underneath the jack pad has to reach far enough in to get to the chassis.
Cheers