Get a RID module and attach it, then you can be legal in the US to fly . . . from another post in the SparkPilots forum . . .
One pilot had a couple of RID module specs and compared to a Flytron strobe (very small lightweight strobe light) . . .
"CubePilot's product measures 25mm (0.098") x 13.75mm (0.54") x 3.5mm (0.14") at 10gr (0.35oz)
Dronetag BS measures 17mm (0.66") x 14mm (0.55") x 5mm (0.19") at 3gr (0.35oz)
For comparison, my Flytron strobe is 20mm (0.79" x 16mm (0.63") x 8mm (0.31") at 4.5gr (0.16oz) and attaches to the RH aft prop guard with 3m Dual Lock velcro, so unless the module has specific placement requirements, I'd expect it could be attached similarly."
Hope that helps, the Spark is a very small craft to get anything extra on, but with those size above it should be easy on the other larger aircraft others might have.