These are usually called standoffs. Digikey has many
types
and sizes. Give me material and thread sizes and I can
give you a digikey part number.
A tip on these -- buy them by the thousand. They are expensive in
small quantities, but you can get them in bulk on eBay, etc.
The main parameters are the size of the fastener (#4, #6, #8), and
whether you want male or female ends, and threaded or not. Lesser
parameters determine the length of the threaded post, etc.
Vince