Chris:
How far back do you want to go?
This is probably the most "original" .500 Express packet you will find!

String-tied brown paper. Marvellous! (...and pretty easy to reproduce!)

This one is more recent. Note that these early BP packets held 10 cartridges, it was only the later Kynoch packets which held 5 rounds.

The later Kynoch 5-round packets looked like this:

Hope you find this useful.