Of interest, as I went down the rabbit hole with this a while ago, is that it’s not too difficult to make custom vac clamp shapes. You just need a plate of Delrin cut to shape, drill out an internal patch way, and lay on a gasket. I haven’t done it, but it does seem easy. 

Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".