Here's what I propose:

Each station distributes a Daily Inventory Catalog. Players could "subscribe" to this catalog, for something like 20c per 'issue'.. or more, the actual amount doesn't really matter, so long as it's not "free"... I guess. Maybe it could even require a trading license.

Since the catalog is merely an inventory list of what the station has, it's published in Real Time from the station 24/7. However, in order to receive a copy, you must be in the same sector (or system?) as the station. Maybe even the 'surrounding 8 sectors' could quality as well.

The catalog should be viewable in flight, and shouldn't "take up" cargo space, since it's electronic data stored in the ship's computer.

This introduces another limitation: Database size, so that way you can't horde dozen's of catalogs at once, ships would be limited on the amount of information it can store, and would vary between different ships. An inventory list doesn't really take up much 'space' though... so, it's not exactly realistic unless there's all sorts of other information about each item.