Rick....
Most supermarkets carry it in the sugar section. It has a few names, one of which is Sugar in the Raw.
I am not a big believer in using Turbinado. The biggest reason folks like to use it is because it has a higher burn point....about 372?. Normal sugar has a burn point around 325?. So, my question has always been, if we are cooking low and slow, why pay all that extra money for something that you really don't need?
I have cooked many batches of ribs that I sauced BEFORE and DURING cooking(Carson's ribs technique). They were cooked for 6 hours and the sweet sauces never came close to burning.
Many will tell you to not sauce until the last 30 minutes. This is supposedly to prevent burning, but again at our low temps, the burning point is never a factor. Now, if you are high heat grilling, then, yes, better not sauce until the final few minutes. But, for low and slow cooking, save your money.
On the other foot, many find it has a unique flavor. So, in that case it may make sense.
Good luck!