Kirk LP-61 replacement foot for the Canon 100-400 ISL II zoom lens. This foot
is a little longer than the Canon but more importantly, it is an ARCA Swiss mount
compatible. Nicely machined out of aluminum, it screws into the bottom of your
Canon zoom with the supplied allen wrenches. $80 new from B&H + tax.
$45 shipped to your door (continental U.S. only)
I purchased a very similar replacement foot for my EF 100-400L II from Amazon, $34.99 delivered. It too came with two allen wrenches but neither has a T handle.