Go to the doctor’s office! No, really just use the same tissue paper placed over that 1960’s era Naugahyde exam bed they use to keep the evil germs away.
Tissue rolls are cheap, you get tons of it for pennies and you can trace over your equally fragile patterns (vintage or just abused) with a pencil then don’t feel bad about cutting it out and throwing it in the fireplace when done.
Seriously, you’ll have plenty of this stuff to go around so don’t feel bad about cutting your traced pattern. I like to use mechanical pencils for the tracing. If the pattern beneath isn’t easily visible, use painter’s tape to attach it to a sliding glass door, then use the same tape to attach pieces of the exam paper over top.
These rolls are perfect for altering patterns too. Yolk too big? Pant leg not wide enough? Adjust your transfer and if it doesn’t work out, just trace another copy of the original and try, try again.
Tip: Be gentle with the painter’s tape, it may be meant to not stick too much, but we are talking about tissue paper here so it might help to have some clear tape to repair your original or reinforce your original tissue pattern if needed.