If you are saying that your requirements call for the Time Capsule to broadcast a wireless network signal for your devices, it can only do this with a wired Ethernet connection at the Time Capsule WAN "O" port.
So, you have two basic options:
1) Exchange the current Jetpack for another model that does include an Ethernet port. This is the simplest solution, and also the most reliable solution.
or
2) Try Using a wireless bridge like an AirPort Express to "join" the wireless network that the Jetpack is producing. The Ethernet port on Express models A1264 and A1392 are enabled when you do this, so this will provide the Ethernet connection that the Time Capsule needs to create a new wireless network
Note.....option 2) is not foolproof. If you decide to try this, expect to restart the AirPort Express and Time Capsule a few times a month on average.
Used A1264 AirPort Expresses are readily available for $30-40, if you don't want to spend $100 for a new Express.