avidvaper.com is now the only place stocking cisco lr 306s. some other vendors may have old stock of legitimate cisco's, but when they run out, they are out. av is cisco's site, and he is no longer selling them wholesale.
i know that at least one earlier batch of genuine cisco's did not have "cisco" imprinted on them. i can't recall if they had no imprint, or maybe it just said "LR" or "1.5" or something. not sure exactly, although I do know that I read a post made by Cisco himself, stating that some of the earlier ones were not stamped the same.
as far as the burnt taste, it could also be that you didn't prime it enough before using it the first time. cisco lr 306's come PRIMER-LESS, unlike most attys. so, it takes even more liquid to prime it than would be necessary for an atty from which you blew out the primer. A new one needs a good 6 drops, wait a minute, and add 2 more.
Also, i've found that during their first day or two of use, the cisco 306s are juice monsters, and really need to be kept constantly wet to avoid a burn taste. After they are broken in, i find them to be much more forgiving.
Lastly, because of the exposed bridge, it is very easy to remove the wick from these. When nothing else gets rid of the burnt flavor, just pull out the wick. You may experience a slight decrease in performance and/or an increase in leaking (though, for some reason the only 306 i've de-wicked actually leaked less for some reason after de-wicking), but it should get rid of the nasty taste.