Attaching gear reduction to Durston rolling mill

I purchased a Durston 100mm combination mini mill with extension
rollers last year. I wanted to get the same mill but with gear
reduction, unfortunately it couldn’t be shipped through the post
because of the weight, so I settled for the one without the gear
reduction box. What I’m wondering, is if the gear reduction box can
be purchased and added as an after market improvement? I haven’t
seen any on this on the Durston site itself.

Thanks!