Here's a very inexpensive trick I sometimes use to vacuum seal Ziploc bags (YMMV!)

Instead of an electric- or battery-powered gizmo, I use a drinking straw - usually the sort that bends, but that's beside the point. Any drinking straw will work. After pushing most of the air from the plastic storage bag, I'll insert one end of the straw to the side/end of the ziploc bag so it's just below the 'zip locks' and close/seal the bag all the way to the inserted straw. Then, I'll suck as much leftover air from the ziploc bag through the straw (please, no vulgar, obscene & otherwise unfriendly comments!!!). While maintaining that 'vacuum', I'll withdraw the straw and quickly close that little bit of the 'zip' lock for a full seal. I hope this makes sense? Sky