if you have a ship, say a z-95, and they do not come with hyperdrives, is there a printed system by which you can either retrofit it for internal or external hyperdrive (like the jedi hyperspace rings in ep2)?

The attachable hyperdrive rings are spoken of in Stay on Target.

Stats are in eote core. F&D as well I believe...

Do you mean in game as in they have to find the parts and time to make the necessary changes or whether to let them have access to a hyperdrive capable Z-95?

EotE page 255 - The Syliure-25 hyperdrive sled "Designed to add hyperspace capabilities to smaller ships without hyperdrives." It gives a class 2 hyperdrive to a sil 3 ship, good for five jumps.

Theres the Z95 Heavy which comes with a class 2 hyperdrive + astro droid from memory, so that's just some extensive re-engineering to get it done- well beyond the average 'mods' kind of stuff people strap up, but a good slipyard, time and plans should see them be able to cobble one together

i reviewed the stuff in the sourcebooks. hyperspace rings could use better definition. saying that they have 5 uses seems a bit odd. i mean, having only 5 pre-programmed jumps makes a bit more sense, especially it the ship doesn't have an astromech to program them. but 5 jumps before non-use at a cost of 10,000 credits does not seem very cost effective for any consumer. i mean, for the supplier it makes sense, as it causes the consumer to buy more... but who would buy such a costly hyperdrive for so few uses?

I thought that they could be refurbished for a fraction of their cost and returned to service after using them five times. I'd even say that the companies that sell them offer such as part of a service plan to ensure constant income.

I interpret the "five uses"-thing to mean that they are pre-programmed with the coordinates of 5 jumps; that is, 5 systems between which they can jump back and forth freely as many times as the owner wants to. If you're going someplace other than those 5 systems you need to hook them up to a nav computer (either aboard a larger ship or at a starport) and delete one or more of those 5 coordinates and input new ones.