As much fun as it is to shop for products online, sometimes it is very gratifying to be able to make something the exact way you want to.
Below are a few sites I have come across that provide free patterns and a video that shows how to make a walker tote bag.
Free Patterns:
Free Wheelchair & Walker Bag Patterns - 20 designs from SewingSupport.com: http://sewingsupport.com/sewing-how-to/free-patterns-and-projects/bags/wheelchair-walker-bags.html
Sew a Walker Bag to Carry Needed Items by Debbie Cosgrove, About.com Guide: http://sewing.about.com/od/healthbeautyitems/ss/walkerbag.htm
A Walker Bag with a Professional Touch, sponsored by PaulaJuliaDesigns: http://www.pauljuliadesigns.com/freepatternsandmore/2011/07/10/a-walker-bag-with-a-professional-touch/
YouTube Instructional Video:
http://youtu.be/zqfmuXQ_moc
If you have trouble threading needles or need magnifiers to rip seams, visit Vital Home Store's Sewing Aids collection for a few products that may help. The collection includes both the HEXE and INFILA Needle Threaders, as well as a Seam Ripper with a 5x magnifying glass. New products are being added weekly, so check back.