Not sure how many per day you are making, or how many employees will be doing this every day, what kind of machinery you have or will use, if you are doing this in a garage, basement, or a 100,000 sq.ft. plant, and I'm not sure how much or how little a 7.5" base made of mdf will hold, but you can go to your local machine shop and have a hole saw made to your specs to fit a chuck for a drill press if that is what you want to do.
Remember in production, you want as little waste as possible so a lot also depends upon what size wood you are working with. If you are using linear boards, then you probably need mdf stock that is 7.75" to 8" wide to get a good clean 7.5" piece of wood with double sets of rollers on either side of you drill press, assuming this is some type of poor boy operation(or else we would let the plant engineering staff figure it out).
It also depends upon if you want a straight edge around the base or some type of routed edge, then you may want to use a router to start with or have a two stage operation with a routing afterwards but I don't think mdf will route very well so forget that idea.