"wondering what would be a good choice"
Depends who you ask
Oil is like a donut .... everyone has their favorite.
You can use any motorcycle oil. You can also use an automobile oil but most auto synthetics have friction modifiers in them so you must be careful which one you chose. On an oil container you will find a circle containing the grade of oil (20W40), the API
designation (SG) and at the bottom it may have the words "Energy Conserving". Don't buy any oil that has "Energy Conserving" in the bottom circle for your R* as it contains high levels of friction modifiers which can cause clutch slippage.
Check out http://motorcycleinfo.calsci.com/Oils1.html
for some info on oil
Don't worry about the residual oil in the crankcase when you switch over. If you have a problem on the road and can't get syn, you can even add dino to the syn. Just change the oil when you get back home.