SCTP is like IPv6 - it has many clear advantages over its predecessors,
and has been predicted to replace them for nearly 10 years, but is still
seen almost nowhere. Just as IPv6 is only found either on specialised
or highly technical local networks, or tunnelled over IPv4 for wider
networking, SCTP is only found on similar local networks or tunnelled
over UDP.
There are almost no off-the-shelf routers that handle SCTP explicitly
and are sold at a sane price tag. (Of course trunk routers just pass on
the IP traffic without concerning themselves with the protocol inside.)
Windows has no native SCTP support. Thus there are virtually no
applications that support it. Thus there is no incentive for MS to
support it in Windows, and no incentive for makers of small routers to
support it. Rinse and repeat, going around the circles as much as you
want. Chickens and eggs.
The trouble is, while SCTP has many clear advantages over TCP/IP and
UDP, and could replace both of them, in almost all use-cases you can
make either TCP/IP or UDP work well enough. Patching, encapsulating,
workarounds are all lower cost and fewer changes than switching over to
something better.
So while you are right to think that SCTP is a superior technological
choice, you can expect that none of your customers will have any
interest or ability to use it.
Having said that, if you still want a router that is SCTP aware, I think
the best bet is to put one together yourself. My primary suggestions
here are pfSense running on an x86 box (since you like BSD), or OpenWRT
running on practically anything from a cheapo home wireless router to a
powerful rack server. They are both straightforward to install in most
cases.