I think you are being very reasoned in your approach. I have been accused (by a couple of former forum members here) of being a "nanny" (putting it nicely)....about this stuff. But I've also seen the aftermath of the "here, hold my beer and watch this" crowd....I get to suture those guys up, splint their fractures or administer the CroFab....so I really do tip my hat to your diligence.
And you're correct about the costs involved. The average keeper can not afford it, but since it is a pharmaceutical, you'd need a prescription (or DEA/medical license) to obtain it. Then, you'd have to consider would the ED you go to even give it to you since they were not the originators of the medication (liability issues)....If the reptile zoo let you use their stock, it would likely be a donation, out of altruism, no medical insurance company would reimburse an outside party in that manner....maybe the zoo's insurance might, idk...
You might reach out to Jerry or to Willow on the forum here...they may be able to answer the question in a more practical manner....even in a PM. I am speculating simply from the ED physician standpoint... not so much from the keeper standpoint as to what most tertiary ER facilities can take care of.
I hope you never have to find out!