Crowbar
I agree it seems bizarre that they havent got an adaptor plate.
Other aftermarket suppliers obviously have. S&S are missing out on a niche market, although small it is growing and there are more m3ws in the States now.
Perhaps a more direct approach would let us understand what options are available.
Any m3w owners nearby S&S? who could approach someone at S&S who might know if and when alternative filter covers would be available?