Might be easier said than done though. It's very expensive & challenging to get your hands on it as a private party. And if you try to go thru "back-channels" you also have to worry about it being a fake. Expensive & hard to obtain things are at the top of the list for counterfeiters to "make" & sell. Just saying- you could be paying top dollar for corn syrup.
And call me "old-fashioned" but I'm not so sure that a scarce commodity like antivenin even belongs in the hands of a hobbyist that just wants to keep a deadly species, over & above keeping the stuff available for those whose legitimate work (like agriculture & construction projects) puts them at high risk in the countries where these snakes are found naturally. It just doesn't.
To "put that shoe on the other foot"- how would it feel to be camping on vacation & end up with a life-threatening rattlesnake bite (from one of the species with more neurotoxic components in their venom), only to find out there was no anti-venin available because it was sold out of country to the highest bidders? Not so good...