Amazon gift cards are not available any longer. You can choose prepaid MasterCard options instead, and use that for your Amazon purchase.
When items are out of stock for the Rewards program they are temporarily removed from the catalogue. If/when more stock is available, you should see any 'missing' products back in the catalogue and available for ordering.
If you're like me and wanting to use your points for Amazon GCs, I would suggest checking back periodically to see if they are restocked and re-added in the future.
I followed this advice only to find out I didn’t read the small print — the TELUS Mastercard is only valid for use in the TELUS stores so you will not be able to use this at places like Amazon or any other retailer. Just wanted to warn anyone else before they made the same mistake I did. They should have just made this a TELUS store giftcard as it is misleading but I did forward my comments about that to them.