Where can you get the rigid plastic sleeves?
Most coin shops will carry a variety of sleeves.
You can also check online for papermoney supplies.
For example Colonial Acres Coins in Kitchener stocks them
You can call them for prices and types available as well as costs if picked up at the store or sent via mail.
You can also go to most coin/papermoney shows where it is common to have a few tables selling supplies.
Hope this helps