Direct response: Purchase an E1 card and put it in your server.
Explanation: Digium makes them (and they arguably created Asterisk to sell those cards) as well as Sangoma and likely others. The market changes regularly, but there are always options for where you can purchase an E1 or T1 card to convert the signal for use in Asterisk.
Advice: Seriously consider putting the E1 or T1 card in a separate "asterisk only, clean install, no other software" server. It need not be huge or powerful. It's ONLY job will be to convert the E1 signalling to SIP for transmission to your Vicidial server(s). This would allow that server to operate untouched and unchanged ... forever. Make sure the hardware is solid, redundant power supplies are cool. Skip building any logging or call recording into it (or at least turn off logging after it's up and running, to avoid HD bloating over time).
An advantage of this is that the sellers of this hardware specifically create it to work with Asterisk (Not Vicidial). So a vanilla/stock asterisk server allows them to work through any issues to get it "online and working". Keeping it that way will allow any future issues to be as easily resolved by the vendor (in case the card dies, which doesn't happen often, but will still be a thought if something goes wrong).
Then when your Vicidial or other production server has a HD failure or requires customization or upgrades, there's NO impact on the machine with the E1 card. This tends to make it much easier to upgrade, reinstall, route around or otherwise deal with call pathways over time. As if the carrier were still SIP.
Not kidding: We've had clients leave this E1 Only server behind in a telephone closet and route their calls through internet to their new location for several months after giving up their location. Then return one day to sneak in and get their equipment and cancel their internet and E1 service. Nobody knew they still had equipment in the closet, much less that it was actually still in use routing calls to their new location until they telephone contract ended.