A lot of folks here say the NGK BPR6ES is the best. Mine fouls twice a year, but after cleaning is useable.
A few folks say they have had good luck with Champion plugs. I got myself a couple of RN9YC.
and N11YC, which are hotter. I always carry a spare plug with me, because a single cylinder engine is not very tolerant of ignition issues when cold starting. My riding pattern tends to foul my plug every 6 months or so, only 20 minutes of riding at a time, low speeds, lots of idling at traffic lights, so I'm going to a hotter plug for general use, and I'll switch to a colder plug for the few times a year where I'm riding at higher speeds on open roads.
If your machine has the a sparkplug cap that takes the small diameter, threaded post, you have to pay attention to whether the plugs you buy have rounded nuts that screw off to reveal the threaded post, or don't.
I had a factory cap failure, when arcing occurred where the cap screws into the ignition wire. It hadn't been screwed in all the way at the factory and the resulting arcing opened the resistor inside the cap, killing spark. So, I'd recommend making sure that the cap is screwed on tight, on the wire, at minimum.
If you decide to upgrade the wires, or the caps, you can. Both can be improved on. You'll want to preserve some resistance in the secondary. The factory has 5K ohms in the cap, and the spark plug is also a resistor type, I think that's 5K ohms also. I'm pretty sure you can get away with resistance in one or the other, but having no resistance in the system is said to possibly cause EMI interference with the EFI system.