A right handed safety (mounted on the left side of the frame) is usually what comes on most 1911's and S&W should easily be able to do that for you. You might want to call their customer service and ask them what they would charge to do that.
If they won't do it, then ask them to send you the part and either install it yourself or have a LGS fit it for you. There is some minor fitting usually involved, and I do not know how handy you are with a file and the pistol's disassembly and reassembly.