The EX300 has a chainguard/hugger that's an almost-bolt-on, and only $30 from Partzilla.
Just drill and tap (M6) two extra holes on top of the swingarm and it bolts right on (see the silver socket cap screws in the first pic). In addition to the mini-hugger, it also has a notch where the front of the tire comes near the chainguard, if you want to run bigger tires.
The hugger is
36014-0555 and the two additional screws on top of the swingarm are
92154-0918. Or you could use double-sided tape or zip-ties to hold it on, if you don't want to add those holes (it's probably much harder with the swingarm installed on the bike).
It's obviously got a much smaller fender section, so I'm sure some people may not like it as well. However, it's a direct fit on the stock chainguard tabs and just a bit of extra securing on the other side/front. A little better in some ways, a little worse in others. Just another option that some may like...