Okay, replying to Kell this time so I don't ramble in another thread. Yes, the crazy lady is back.

Boosters Kell!
Also known as inserts, stuffing. You can put them in a fitted nappy to boost absorbency, or even in an AIO to make it more absorbent, but they are the heart of a Pocket nappy!
One type you don't need to fold, trifolds, you generally fold to fit, usually in thirds, hence the 'tri'.
You can use anything, folded up facewashers, rags, a cheap chamois from a $2 shop. Most people probably buy or make their inserts though. Some of the more common absorbent materials are:
Microfibre: Very absorbent, in fact, don't let it touch bub's butt, cos it can dry out their bottom too much and irritate it! Some microfibre boosters have a microfleece top, so you can lay it close to the butt, like if you're boosting an AIO. The ones that don't need to have a layer inbetween, so are good in a pocket nappy. Microfibre can soak up wee very rapidly, great for those all at once wees. Dries very quickly.
Hemp: Absorbent, can touch bub's butt, natural material, so safe if bub reacts to synthetic materials. Usually dries more quickly than bamboo.
Bamboo: Slightly more absorbent, therefore takes a bit longer to dry too. Also a natural material. Can be more expensive than hemp.
They're the main booster materials.

Stores to buy from?
There are a few BellyBelly people who have Modern Cloth nappy stores, you can probably find them in the MarketPlace or something? Should mention them, since they pay to advertise!
There are other Australian cloth nappy superstores online, if you want to know where your friends shop, I guess PM to find out?
But Kell, if you've found them cheaper from the US, and shipping isn't too much, then go for it I reckon!