Looking for Fast RS-232 or RS-485 Interface Cards for Windows

I have a module that is usually bundled with a master module, which we now want to use unbundled. The module uses an RS-485 interface. The problem is, by default, the module runs at 1.25 Megabaud, which is not one of the "standard" speeds that most integrated PC serial ports run at.

For my own uses, I can whip up a relay system using some microcontroller demo boards I have lying around开发者_开发知识库, but we also have a desire to make this usable for people without mad embedded skills.

So, does anybody have experience with, e.g. PCI-to-serial cards that can run this fast? It's fine if we end up with a fast RS-232 card that then goes to an RS-485 converter, although it would also be cool if they actually had a PCI-to-RS485 card that worked standalone.

My typical go-to place for stuff like this, B&B Electronics, only has cards that go up to 921 kbaud.

If you can spend the big bucks, National Instruments has a card that can do 57 baud to 3 Mbaud.