Oh love :(
As a (gradually recovering) emetophobe, I really share your fear.
Preparation: when recovering, stick to the BRAT diet - bananas, plain rice, apple (cooked is better, and pear is good too) and plain toast/crackers.
If you can, get some dioralyte sachets as they help after dehydration.
Grab any old towels and keep them by the bed.
The absolute most important thing is keeping your babies hydrated if they get it. NOT big gulps of water - a teaspoon every 5-10 mins is better and will be more likely to stay down. If your BFing, your milk will be great too.
A couple of things I have learnt from my own panicky threads. IT WILL PASS. It is horrible and unpleasant but it is not forever.
You might not get it. As an emetophobe I catastrophise every time anyone near me is sick, assuming it is norovirus, but it could be anything else like something he's eaten.
Also IME the nausea bit for me is worse than the actual being sick because by the time I am sick it is welcome relief.