Using a hand operated pump you got to have planned to have 99.5% perfect seals and then use lab grease on all fittings. A brief pulse of negative pressure at the filter helps but not by much!
Nothing I have was store-bought, all cobbled together, I went through four or five rubber stoppers to get one drilled correctly to accept the buchner funnel, and even at that since the funnel spout is tapered and the bore straight it still kicks to one side and wants more to leak than not. And trying to DIY that with the silicone acid-resistant ones would be silly expensive.
I guess what I am saying is have your ducks in a row before advancing to live chemical processes - 20 minutes of rapidly squeezing the grips of that hand vacuum pump will make a believer of you.