I'd like to find a few panels for the centers of throws/wall hangings,for Fall & holidays.Have never bought one & no idea where to find them on line. Any ideas?

most quilt shops carry a few panals, they are quite popular. a few places to check out...
fabric.com
bear paw quilt company
the cotton patch (in east tawas, mi)
homestead hearth
dakota cabin quilts
keepsake quilting
hancocks of paduca
joannes
ben franklin crafts
there are tons more but that should give you a place to start.
if you join the on line (FABSHOPHOP) you will find a list of over 200 quilt shops, which gives you a huge resource of places to search for what ever you may be in need of at a very wide range of prices and shipping policies.

My favorite panels are usually made by Moda.

Moda is good and Wilmington has a lot of nice ones, also.