Get a tabletote they are the best https://www.amazon.com/Tabletote-Portable-Lightweight-Adjustable-Table/dp/B0001EMA80

Some ppl have started using these levit8 ones but after my testing I concluded that all of them were either to short or wouldn't fit in my (already quite large) backpack https://www.amazon.com/Levit8-Coral-Size-portable-standing/dp/B01LY0CE5C

Also Scotty P thinks you should use a music stand but I can't imagine how you would transportation one that was even remotely sturdy enough to hold a laptop