What do you do if your latest hack needs a little piece of fiberglass fairing? Well you do what any experienced RC Helicopter pilot does, you use your vacuum press.
Whether it’s fiberglass, carbon fiber, Kevlar or even laminating wood. You can use a shop vac and electric grill to build a set up like this for forming plastic.
Or build your own vacuum pump if you need a longer clamp time for say veneering wood.
You might try Space Bags but check that your resin won’t stick to the bag first