Joe Rocket did make one but they are out of business. It only added a extra 250ml or so of oil. I have posted about this before and the best solution we could come with was a Dakar style bash plate with an oil tank instead of water and plumb it into the oil line using the Joe Rocket style adapter. Which was a replacement oil filter cap with an inlet outlet and a remote oil filter. It was mentioned that the oil tank should be kept at around the same height as the crankcase oil level to avoid wet sumping. However if the oil tank was higher a one way valve may prevent this. I'm no expert on oil pressure and the internal needs of the 650 and some one who knows more could chime in. My original idea was using the underseat fuel tank, but wasn't sure how heat proof it was. Although I have seen bikes with plastic oil tanks, not all plastics are the same. Otherwise I thought of getting an oil tank made from alloy. If I recall the Joe Rocket oil coolers were mounted in front of the radiator or under the seat, so I would assume they had a one way valve to stop oil running back, so my original idea came from replacing the JR cooler with a larger reservoir. The other question was if the oil pump had the pressure to pump higher than the crankcase.