You can probably build a carbine by watching those sites for a lower, then watching BCM's site for an upper. G&R Tactical often has carbine lowers but you'll need to order a stock too.
If you're looking for a rifle, that's a little harder. I think Ranier had some last time I checked, at least lowers with a rifle stock installed. G&R has them listed with a Magpul rifle stock, but last time I checked, they were out.