Panel Joggler/stepper tool

Hi Guys, i'm gonna make a start on welding up my 300 Series Disco 1. I'm wanting to do the job properly and i'm gonna be chopping out the rot and want to step the new metalwork in so i can seam weld the edges and spot weld as well. Any of you chaps got a joggler/stepper tool that i could make use of to save me forking out £50 for a new 1.

Thanks in advance

Dave