Leak Stereo 30 integrated amplifier

Hi guys
Is there anyone who can tell me what size banana plugs will fit the speaker inputs for this amp?
its a very unusual setup with one large and one small hole for each speaker connection.  The owner has no way of measuring it and the original plugs are very hard to find.
At the moment the owner is using matchsticks to hold the cables in which is far from ideal and she doesn’t want to convert it to new binding posts due to cost.
Thanks
Happy new year
Ed