Copper is what I would like to use, I'm not running a business on it so a one time purchase, although pricey, is one of those things I could get over eventually. What would you use to cut it though ?
The commercial services use a laser - not many of us have one of those! It's also possible to use a plasma cutter or a CNC mill, but those are not typical DIY tools, either. For the shape shown, a bandsaw seems like the most practical home-workshop option to me (although I don't have a bandsaw, either - I do have a scroll saw which would likely work with the right blade), with drilled holes. Unless there is some detail of the cells which is not apparent, you can make the plates much simpler in shape by placing the cells in alternate directions, so the plates are just rectangles connecting the positive terminals of one group of 7 cells to the negative terminals of the next group of 7 cells right beside them.
I assume that the separated "fingers" of the plates shown are used to allow some movement between the terminals of adjacent cells, to accommodate thermal expansion and contraction of the cells and thickness growth over the life of the cell; the same thing could be done with rectangular plates.
By the way, you're talking about 7 cells in parallel, then some number of 7-cell groups in series. If, for instance, you are connecting 21 cells this way (it has to be a multiple of 7), then you would have "3S7P", meaning 3 groups in series with 7 cells in parallel in each group.
I also noticed that all of the online references that I found for ePLB-C020B cells are bare pouch cells, not mounted in plastic frames and equipped with threaded terminals as you appear to have.