You really should not need Sewer's Aid. Make up a small sample and sew through it to see if your needle gets gummy; it probably won't. If it does, you can clean the needle with alcohol on a cotton ball. It is not an "essential" for applique!
You can order Sewer's Aid from Amazon, but honestly I wouldn't bother:
http://www.amazon.com/Sewers-Aid-1-2...dp/B000YQKO6K/