For PayPal on the main page at the left click on Rewards, then Denominations at the left, then Gift Cards - $25. When sorted by most popular Paypal is the second item showing for me. PayPal is not available in smaller denominations.
For most denominations Amazon.ca is the 2nd or 3rd item listed when sorted by most popular. Look for white card with gold stripes at the top and bottom. The Amazon.com cards show in black. For $100 and up you will need to look further down the list. To make sure they show near the top of any of those lists, change the sort to A-Z.