Recommended way of receiving syslog messages after an outage

We primarily use Cisco ISR routers which send syslog messages to a centralized collector. The issue of course is we never "see" the interface or BGP flap messages because, well, the single WAN connection is offline when those messages trigger.

Does anyone know of a solution to this that doesn't involve setting up a local syslog collector? Even something as small and cheap as a Raspberry Pi would pose challenges for us. We have buffered syslog messages configured so a show log will produce the missing output, but it can't reach us during the outage.

Is there a way to re-send buffered syslog output once the WAN connection comes back online? Would using TCP syslog instead of UDP syslog help at all?

Any ideas or solutions would be appreciated.

Thanks