Are you looking to by board and pieces separately? Because the easiest way would be to buy a travel set. My 12" travel sets have 30-33 mm squares, so maybe a 14" travel set would be fitting.
I have been looking for nice wooden pieces for my 40mm square chess computer for a while and found it rather hard to find pieces, that have some detail and preferably don't come with the ubiquitous German knights. Thankfully I found some vintage chess pieces. King height is 65mm, so 70mm sounds rather large for 35mm squares.
My 70cm Chavet king definatly looks kind of fat on 40mm squares. My 33mm square travel set's king has a height of 65mm. Obviously it also depends on factors other than height. The computer itself came with a 70mm king that was rather slender for its height.
If you are looking for pieces only, Philos offers chess pieces with a king height of 65mm. "Philos Napoleon" has some kind of Lardy-ish knight and "Philos Artus" has a German knight.
I'm planning to get a chess board with 35 mm squares for analysis purposes. Where can I buy pieces? Any suggestions are greatly appreciated.