That depends on what your definition of "a small number" is and what you plan on doing with them. You can only buy them in powers of 2 with a minimum block of 256 and there are many brokers happy to facilitate a sale. You can also get them assigned (in a limited and often delayed fashion these days) but only if your intent is to actually use them as a new entity (or if your intent is to try to game the system for money then that's its own path with its own pitfalls). Once you have them you'll also need to pay regular registration dues while you hold them. If you plan on using them you'll need a BGP ASN and a peering relationship or a provider/carrier willing to advertise it under their ASN and then pipe it to you. AWS supports this and calls it "BYOIP". Advertisements to the internet are made in chunks the same sizes as you can buy.
The above is slightly simplified but it should give you the gist.
The above is slightly simplified but it should give you the gist.