The pivots for a Juice need to be 1/8" diameter. For the KF-4 you need 1" long pivots --- I got mine from a USA site, but shipping and import taxes bumped up the price. Just recently I got some 1/8" pivots from a European supplier, but these were shorter and only just long enough for the 'Slim Jim' one layer mod (and I had to grind down the screws as they were too long). Interestingly, the US pivots were tight in the Juice, and I had to rub them down a bit to get them to fit, whereas the European ones slid into the holes more easily --- maybe different tolerances?
I did have a cheap highstreet multitool with pivots and screws and I used the pivots from that for my Squirt mod --- I suspect these were 3mm whereas 1/8" is 3.175mm. If you are really in a bind, you could use a M3 3mm nut and bolt to hold the Juice together.
I used a Dremel to drill out the original pivot --- I ground out the dome mushroom shaped top and was able to push the pivot through --- it helps once one backspring is loose so you can remove the other backsprings, since the tension from the backspring tends to stick the pivot in place. If you are careful you can save the scales. But sounds to me like you may only need to remove one pivot.
Once you have the new pieces and pivots in place there's a technique to get the backsprings in. For the inner layer I insert the backsprings so they are sticking out from the non-plier end and squeeze the pliers closed so as to give a push on the partly inserted backsprings, then (heavily) tap down the ends sticking out. There's a nice strong sharp click as the backsprings go into place. If you need more advice, I can post some pics.
Good luck.