There are many of us who successfully use a single needle to draw up the vaccine, immediately return bottle - sealed with tape - to the fridge, and have been doing so for years.
Remember that the advice to use and throw away comes from the manufacturer, who obviously wants you to buy as many bottles as they can get away with.... also if the vaccine is used in the field and then stored on the Farmers 4 x 4 dashboard it will obviously go off...
You can also get the injection guns, where the bottle stays connected to the gun and can be stores like that, just needs a needle change for the next time.
I do Heptavac for the sheep and Lambivac and Ovipast for the goats, but I have higher numbers than you.