Why are you looking for a vacuum easel for alt. process? For a silver gelatin, I could understand since the negative is projected. But for alt process, you have to keep the film flat against the paper, which means the vacuum won't work on the film on top, just the paper on bottom. That means that you'll still need a sheet of glass over the top. Even vacuum easels that I've seen in print shops that use contact printing as a method have glass tops, and just use the vacuum to secure oddly shaped mediums, like stretched silk screen frames where the frames have to be exposed vertically. And they wouldn't work well with paper, as it's too thin and would likely crumple under vacuum, since the back is basically just a loose rubber sheet.
I think your best bet is to stick with the contact frame and figure out a way to use a more culminated light source. Also, turn the negative over so that the ink or silver particles touch the emulsion on the paper. I've never had issues with sharpness in my 11x14 glass contact printing frame. Maybe you just need a new contact printing frame.