I agree with Sharlene, Julie and Barb
Either Papaermart or Nashville Wraps are both good sources for tissue paper and other packaging supplies. I find that Uline tends to be a little more costly. However it depends on what type of tissue paper you are looking for (printed, colored, recycled, etc..)
Bags & Bows is another company that stocks gift and packaging supplies that might be worth checking out.
www.bagsandbowsonline.com