Whether you want a griddle for your stove-top, grill, or camping gear, I am going to advise you to first shop at Amazon, because of their selection. From electric to manual, Amazon has an array of griddles at all price ranges.
Out there in real worlds-ville, there are options -- especially if you have got time to wait.
One thing you could do is take note of estate sales, garage sales, "and the like" in your area. Early birds to these affairs might luck into a griddle or two.
Or you could get engaged. My wife and I were gifted the "family griddle" by her parents at our Jack & Jill shower.
(Of course, that one was a joke. Mostly.)
Be sure to hit up you area's Goodwill Store to save money on a griddle. While griddles are occasionally donated to Goodwill, they also sell new, non-electric griddles seasonally.
No matter which griddle winds up meeting your needs, I wish you "good griddlin'!"