On line at sprocket center, puchased new chain and front and rear superlite rsx sprockets. Went for a ride today with new sprockets and very happy with results, runs about 500 rpm less at 75 mph.
I have a 2019 ftr 1200s with bassani pipe and fuel moto flash program and did 135 mph at 8000 rpm in 6th gear, just replaced sprockets and chain from sprocket center which had a 46 tooth rear sprocket, hoping for 140+ mph.