This is page 54 of the manual.I don't know which ones you're referring to. But I guess they might be the ones for the armrests? They should be the same as the ones for the lower side panels, numbered as 25 in this drawing. If this is the one you're missing, it's said to be "M5 x 16 flange button".

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Javier - Madrid, Spain - Commander of Speedy Marmots Bomb Squadron
www.speedymarmots.com