you could press them in a sieve after you cook them.
there are juicing sieves which are sheet metal with a wooden pestle.
you could also take some large flat spoons, remove some solids with one spoon and press the juice out with another. between squishing, sieving and straining it will get done.
A China cap or chinois. The last time I saw this come up I discovered that they ain’t exactly cheap compared to a food mill.
A food mill is the better option, and it’s the best tool for making smooth, mashed, root vegetables* and great for purees, tomato sauce, baby food, etc.
Better mills come with interchangeable bottom plates with different sized holes. Large holes for, say, a raspberry or tomato puree with seeds, small holes for seedless. And no need to peel things like tomato or peppers!
Generally food mills don’t have small enough holes to prevent the teeny seeds from raspberries, etc. from passing through (personal experience). Either get a jelly strainer and bags, or get a food strainer with a berry screen. Be careful though, you will get berry juice splattering around your countertops.