They'd need to source the plutonium for the RTGs for that and from what I've read that's in pretty precious supply. Though maybe we could start disassembling bombs to source it.
If they actually want to do that they'd need to come up with a design more suited to serial production. Not sure how much modification that would take.
If SpaceX ever credibly gets to the point of preparing to send people to Mars I'd think that that would have to happen because how else do you vet your landing sites.
The simple fact that in order to build the first one, you have to build jigs and set up machinery and make a test plan and make test equipment, and debug it means doing a twin would likely be less than 10% of the cost of the original.