You could try kegconnection.com. Although $10 a post is not that bad of a price. Since you are including the shipping into the overall price, why not just wait a little while until you have to order some more stuff (ingredients for your next brew, sanitizer, etc.) and then do one combined order? That should make the overall price more palatable.
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You could try asking your LHBS to possibly add onto their order (the next time they make one) but the down side is it may take a while but odds are it will be cheaper. My LHBS does this and orders from foxx equipment which does have the posts you are looking for.