What kind of connector is on that device?
It's probably the same connector as other devices by Huawei or other manufacturers so if you know what is compatible you may be able to find someone with the right adapter even if it's labelled for another brand of card.
For example the recent Sierra Wireless modems (Compass 597, 598, and 306) use the TS-9 connector made by SMK.
SMK is a popular manufacturer of the miniature RF coaxial connectors that modem manufacturers would use on their boards.
I believe the connector that Huawei uses includes a switch function. That means you must find a perfect fit otherwise the switch will not activate and even though you have it all plugged in the modem will still be using the internal antenna. If you get a cable you will want to test it out by isolating the modem from the antenna. Maybe by putting the antenna inside a can or closed microwave with the antenna outside of the shielding. If the signal doesn't drop when you close the microwave door for example then the external antenna is working. If the signal drops out with the door closed then your adapter failed to close the switch and the internal antenna is still active.
For off the shelf purchase you may have trouble. A dealer specializing in data products that is a qualified installer for Wilson amplifiers would be your best bet. Your not going to find these at a mall kiosk that's for sure.
If you look for "Huawei antenna adapter" on ebay you will find several cables that may be compatible with your modem. You will need to compare any spec sheets you can find from Huawei to find out if the connectors on the models being sold (primarily for units that USA carriers are selling) are compatible with the E182e stick.