You can buy postage machines. However, it would be much cheaper/cost effective to just print your postage using the internet as it will cost you nothing more than the ink in your printer!
Postage machines will weigh the precise weight of your package, right down to the ounce, and allow you to add the perfect amount of postage. On the other hand, if you choose to use stamps, you are mostly guessing your cost and may waste stamps or even add too little postage, causing the parcel to be redirected to you.
You can buy canvas at your local handcraft and arts dealer. There are also possibilities of buying them online such as Amazon, but the postage costs will be big.
Pitney Bowes specializes in postage meters and machines, and offers online postage services.
Postage Meters are postage printing machines or systems for your home or office. Meters print postage directly onto your mailpieces or onto an approved label, which you affix to your mailpiece. No accuracy is required.
You can buy postage online from the USPS government web site. You can purchase stamps for international postage at any post office. And many stores sell postage stamps at their customer service desks. Any US stamp can be used to mail a letter to Canada, as long as the total value equals the 75 cent cost for the first ounce of a normal envelope.
It is BUT the machines that read the stamps might show it as being cancelled and it could be returned to sender or be presented as postage due.
About any bank will do this for you. Also Dollar coins are used as change at government machines such as train ticket machines and postage machines where you purchase stamps.
Pitney Bowes offers a wide variety of printing and postage or mailing equipment. Some of these machines include postage machines, printers, and letter and paper folders. Typically, it supplies equipment used in a mailroom for larger companies.
Postage stamps are not a standard size so there are lots of possible answers.
From a stamp dealer.
Most coin dealers sell them but banks in your area should have some at face value. You also get them as change from postage vending machines and public transportation ticket vending machines such as train platforms ticket machines. In addition the US Mint (www.usmint.gov) has a "direct ship" program that will let you buy the coins in bulk at no extra charge. The only downside is that you need to order 10 rolls (250 coins) at a time.
There are many places to buy stamps on Sunday. Many grocery and retail stores sell books of stamps and most Post Offices have machines you can purchase stamps from when the lobby is open. (I believe that many of the Kroger's grocery stores & Walmart super centers and retail stores sell postage stamps.) You can also buy stamps online anytime at the www.USPS.com website, or you can print your own postage on your computer printer (that is purchased from the website).