Bulldogs World

 they are a little pricey ($21 for an extra large) but they've been chewing on them for over two years and hardly a dent.  I buy them at Bonnie's Barkery in Cave Creek, Az, I'm sure you can google them and they will ship to you if you can't find any locally.  Make sure you get the big ones.

Make sure you get the large or jumbo antlers -

You also dont want any that are cut lengthwise down the middle - The 'marrow' tends to get messy.

I bought her 1st antler chew - (Elk) for $25.00 for about a 6-7 inch piece - that was 3 months ago... and she is still going to town on it -

I was given two Deer antler's (Natural Sheeded ones) that I cut into pieces -  I'm willing to bet each will last for a good 6 months or a year.

I HIGHLY recommend them

one site that seemed reasonable was  "antlerchews"  3 large Elk for $25 -

Different species taste differently also -   Elk, White Tail Deer, Mule Deer, Carabo, Moose (yes MOOSE ! they slice them down to size :)

Well worth the price :)