[Zowayix]

^No, you can't, unless it's the Eon Ticket, which requires Ruby/Sapphire.

All events for Emerald ended at least seven years or so ago, including all Ticket events. Aside from the Eon Ticket, it is impossible to transfer Tickets between games. If you didn't legitimately have the tickets on your game in 2005, you will never legitimately have them. There were never any e-cards in existence for the other three Tickets, not even in Japan, where they were wireless distributions.

Your safest and probably least expensive option, if you don't mind cheating, is to use a device to back up your GBA game cart save onto the computer, and then use an emulator like VisualBoyAdvance to hack the tickets into your game save. Then you can use the device to put the altered game save back onto your computer. There's no risk here, since even if you mess up your save file by altering it, you would still have a backup. Such a device would probably cost around $20.

If you absolutely insist on not cheating at all, then your only option is to get just the Eon Ticket instead of all three/four tickets. You would need an e-Reader (discontinued in 2004, probably like ~$50 by now), the promotional Eon Ticket e-card (a physical card given out in 2003, really rare and probably also like ~$50), and finally an Ruby/Sapphire game, a link cable, and a second GBA. It's also possible, if you have a really high-definition printer, to print out a scan of the e-card.