Wheeled Duffel
Luggage without wheels?
Can you still buy luggage without wheels? Something about 21"x14"x7". Not a Duffel Bag. Softsided for easy storage. Backpack straps would be a bonus.
Although they are getting harder to find you can still find the occasional piece of luggage without wheels. Generally however they tend towards the smaller carry on or duffel type bags (even a number of these have wheels these days) rather than the standard carry on size (the size you mentioned) or larger. What is available depends on where you live. You may want to check at a store specializing in luggage as they should be able to show you what is available. Another option is to look into an actual backpack with the dimensions you are looking for. A final option would be to check stores handling used merchandise for older style luggage. Just one suggestion, check it thoroughly and make sure you clean and disinfect it before use.
When travelling on short trips I prefer luggage without wheels and I was fortunate to pick up one a while back which included backpack straps. Unfortunately it is no longer manufactured so the only place to find one would be looking for a used one.