Gun Dog Supply.com is having a sale on bumpers!
"Lucky Dog" soft bumpers are on sale for $3.70 each, with $5.95 shipping, no matter how many you buy. Available in all colors.
http://www.gundogsupply.com/sofknobplasd.html
If you click on their "Plastic and Rubber Dummies link", in the left hand column, they also have other bumpers on sale.
