Some pound shops have glue guns - I found this out a couple of days after paying a few quid at Wilkinsons!
You can get the sounds back on your keychain by following where the tracks would have gone to, and soldering buttons to the appropriate points on the chip/blob. You can test them by shorting pins, some of them will be used for the sound triggers, you just need to add something else to control them with! I assume you'd be mounting it in a case, so you might be doing that with the other buttons anyway?