OK 235/75-16 is not listed. I glossed over the '85' :(
Anyway with 13800 GVWR I recommend either the 245/75 or the 235/85 depending on what fits best. This gives weight rating of 12,096 and leaves 1704+ that must go on the pin as I am sure it does. And you are probably not at full GVWR. There are certainly other brands besides GY that make these tires.
Generally I recommend the tires should carry the full GVWR and the pin or hitch weight is your safety margin. IMO OEM trailer tires are run at very max rating to save cost.
Could also go with a G rated tires if the wheels are rated 100+ psi.
Sailun S637, or GY G614 have an LT235/85R16-G rated 3750 @ 110psi