Perhaps one option would be to keep an eye out for a good used snap one and sell the magnet one. Could end up being easier than doing the conversion yourself. Or maybe not and would need some luck finding a used one in good shape.
They're not overly common here in Tasmania ... I'd need some luck finding one at all. We bought them in the US.
(As an aside, if you type 'Ortlieb Tasmania' into Google, the site that comes up first, and several times, is the site of a friend of ours.)