H.F.
What usually works for us is a blanket. If he is lying down or sitting with you keep a blanket on you. When he feels like he is going to throw up, just let him go on the blanket. You can then throw the blanket into the wash and clean up your son. It means a little extra washing but it also works as they get older. In the middle of the night, my daughter knows if she gets sick just to throw up on the top blanket on her bed. It keeps it contained so we just have to wash the blanket and not the blankets and a trail from the bedroom to the bathroom.
With a little one, it also means you can comfort them and keep them occupied say with a kids show on television rather than sit in the bathroom waiting for it to happen again.
In the meantime, while he is sick, try to keep him hydrated. To do this, don't give him a lot of fluids give him a teaspoon of water or pedialyte about every 15-30 minutes until the vomiting subsides some. If he holds that down, you can try a little more at a time. The idea is to get the fluid into him and have it stay in him. Also, try the BRAT diet (bananas, rice, apples and toast).
Good luck with your little one and try to stay well yourself.