Inexpensive software bgp router that supports route tags?

Hi all, I was wondering if anyone can recommend a software (preferable), or hardware-based router with an API, that supports BGP with tags on advertised routes? I want to use it for a RTBH feed and having it in software would make certain things easier to automate. I tried Quagga/Zebra but it doesn't support tags. I see Mikrotik hardware routers have an API, but I can't tell if the API supports adding BGP networks, so I need to investigate that further. I can go hardware if I have to, with some ssh/expect scripts, but thought there may be other options that are easier. Thanks, David