Sort of. Snyder togher with Chi have published a paper in 2012 in which they claim to have obtained a fairly similar result using tDCS to vastly improve the odds of solving the nine-dot problem, which certainly strengthens their case (although not as much as if this were replicated by others). The abstract of the latter paper doesn't quite let on how related their two studies are, but in the discussion the authrors emphasize that:
Importantly, our paradigm for brain stimulation is unlike other
attempts for enhancing cognition [...] in that we did not aim
to enhance an existing ability by exciting a specific brain region
associated with that ability. Instead, our stimulation protocol aims
to mirror left hemisphere inhibition together with right hemisphere
facilitation, a condition that characterizes some individuals
with extraordinary savant like skills [...].
They further their point that unusual brain functioning might indeed be the mechanism facilitating the solution to the nine-dot problem with a case report in which the sole participant who did solve the problem sans tDCS aid turned out to have had a brain injury.
I also found a 2012 piece in Wired (covering mainly the latter paper) which is a bit ambivalent whether Snyder's results (in general) could be replicated:
It sounds like a Michael Crichton plot, but Snyder, of the University of Sydney, Australia, says he wouldn’t be surprised to see a prototype of the creativity cap within a couple of years. His research suggests that brain stimulation improves people’s ability to solve difficult problems. But Snyder's interpretation of his findings remains controversial, and the science of using brain stimulation to boost thinking is still in its early stages.
"I think it’s a bit of a minefield," said psychologist Robyn Young of Flinders University in Australia, who has tried to replicate Snyder’s early experiments. "I’m not really sure whether the technology is developed that can turn it into a more accurate science."
Snyder’s earlier studies used magnetic, rather than electrical, stimulation to try to elicit savant abilities. One study showed a change in artistic ability, while another found improved numerosity, the ability to precisely estimate a large number of objects without counting them.
But as of yet, not many of Snyder’s studies have been replicated. Australian psychologist Robyn Young did a study in 2004 that examined the effect of magnetic stimulation on savant-type skills such as drawing, memory, mathematics and calendar calculating. In five out of 17 subjects, some improvement was observed, but most of the findings weren't statistically significant. A follow-up study failed to show any effect of the stimulation.
Young thinks the idea of improving cognition with brain stimulation is plausible, but "there were so many variables involved," she said, such as where to stimulate and how long the effect lasts, that she dropped the work to pursue other research.
So apparently the Snyder studies are difficult to replicate, methodologically... and there doesn't seem to be much interest. Bummer.