If all you want from handguards is weather protection, then Givi do a set for the G310R - the same as fits the Kawasaki Versys 650 and 1000 models. Probably fits the 310GS as well. They are really easy to fit as I have them on my Honda CB500X. Part number is Givi HP4103.
These are just some cheap handguards from Cycle Gear (I see they are on sale for $25 now; we may have paid more) but they are easy to put on and have them on my G310R and my wife's G310GS; on the GS had to move the mirror a little to make room for the bracket. They do help with wind protection and will help with bugs etc; they have holes in them but we just put some tape over the holes from the inside.