I highly recommend going to Target, Wal-Mart, Meijer, whatever your store of choice is and check out their travel toiletry section. There is a chance you will come across at least one of your favorite brands in travel size. They generally run right around $1 per item and are all at or under the maximum allowed in your carry-on luggage. Even if you are driving to your destination, travel size products are a great space saver instead of lugging your 22 oz bottle of shampoo across the country (and conditioner, lotion, body wash,…).
It isn’t my favorite option but if you just can’t live without your favorite bath and body products, you can pick up bottles that are of “legal” air travel size to fill up with those products. If you elect to go this route, make sure you place the bottles in a ziploc bag, in part because I’m pretty sure they are requiring that if you are putting it through your carry-on, but more importantly because these bottles have a tendency to leak. They also are often difficult to remove the product from without either dumping it all in your hand at once or waiting half an hour for one little drop to seep out.