Flanging tools

[ps4330@okc01.rb.jccbi.gov (Peter Schauss x 2014)]

What is the best kind (and source) of flanging tool to put a flange
on a patch section for a front fender.  I bought a patch section
for the bottom 10" of the front fender on my MGB and it looks like
the best way to weld it in would be to make a kind of offset (flange?)
along the top edge like this

            |
            |  <-  Original fender
          | |
          | |
           \  <-  Run a bead with the MIG welder here
            |
            |  <-  Patch section
            | 

Thanks in advance,

Peter Schauss
ps4330@okc01.rb.jccbi.gov
pschauss@aol.com
1963 Austin-Healey 3000 Mk II
1980 MGB