Where (in the USA) can I buy a card supported by isdn4bsd??

[Josh Osborne]

So I want to use isdn4bsd (well, really I want a whole lot of
bandwidth for very little money, and since I can't get that I'm
going to settle on ISDN, and as long as I have to do that isdn4bsd
looks pretty cool, so...)...

...but my local CompUSA/MicroCenter doesn't seem to have an
aisle labeled "ISDN Cards for use with isdn4bsd", in fact it doesn't
really seem to have many at all, and they seem to frown on me
opening them up and looking at the chips on them so I can guess if
they work (and they aren't in the nice clear plastic "boxes" that
let me just look).

Does anyone have any suggestions on cards to buy?  Or better yet
places to buy them from (er, along with the names of the cards!).

I don't really want an external ISDN "router" since my ISP will
only hand out one address for me and while NATing my home network
isn't that painful, I do really like to have (at least one) host
I can traceroute from...and since I need to do a little traffic
shaping I'll need to run all the traffic through my FreeBSD box
anyway...   that really makes me think isdn4bsd fits the bill.  If
anyone has any other suggestions though, I'm all ears.