I think most if not all of the diaper selling websites would allow you to ship to a UPS or FedEx store or anything like that.
I personally try to avoid UPS at all cost, their color is Brown because they are the Diarrhea standard, FedEx is the Gold Standard.
I usually go with ABUniverse, great products with an amazing staff to back the products and provide customer service if anything goes wrong; plus I can see something in stock at the closest wearhouse, order and get my stuff in 3 days.