Here in the UK I would recommend the use of 'Gloy Gum' which is made by
Henkel in England and is a PVA gum of some kind. It keeps very well, is a
convenient strength for use and the bottle I have cost one pound 34p for
142ml. It is slightly coloured, but this is not generally a problem. I
normally have used the same 'gum' that goes into these bottles - it is a
white solid, but I don't think this is generally available. (I don't have
its exact specification - possibly a trade secret.)
Faster than 'gum arabic' which I don't think is available here as
'gum-based glue' but can be bought as gum arabic solid or solution from
artists' suppliers.