Deb - Unrelated to diabetes, I picked up a bike about a year ago, on eBay.  I just wanted something to use to nip to the Post Office, or the village shop, and be cheap enough that I wouldn't have to weep into my Weetabix.  Well, it was before my diagnosis.  
 
It came from a family on the other side of the village.  Their daughter had outgrown it.  It's an adult sized bike, so I dread to think how tall the daughter must be!  It's purple and white metalic, and I love it.  I paid the princely sum of £20.27, according to my eBay history.  What a bargain!  I walked there and peddled back.
Maybe you could try eBay or Freecycle for a cheerful bargain?