[screwdriver]

your origional sliding/fixed stock screw should be long enough for the second option.
the spacer tube could be either a cut down old buffer tube or just a bit of alloy tube that would fit over the guide. whichever way it should be cut short enough that atleast 4mm of guide is poking out the end to fit the folding stock to. when you buy the stock all will become obvious.
a word of caution though if your going to go the spacer route it must be cut perfectly square on the ends