Washers for carb needles
For shimming your carb needles you need to look for #4 washers. These have the following dimensions, listed in decimal, fractional, and metric sizes:
If you can't find #4 washers, try to get an assortment that is close in dimension. Those with 2.5 - 3mm inside diameter, and not being too much larger than 3/8"/9.5mm outside should be fine. As always, it's better to get a few more than you need, rather than having to keep going back to the store.
The washers fit on the needles as shown below. This will raise the needles. Note that the washers shown are only for illustrative purposes; the actual ones used are much thinner.