Sounds silly but...
 

Do ya think there is any way to convert a standard NIC to work like the Broadband Adapter to save money and cuz the BBA is always out of stock (not counting eBay). Just a thought. What do ya think?

The port on the Dreamcast is quite obviously proprietary. The odds of someone converting a high quality NIC card, like a 3Com, so it fits and properly interfaces with the proprietary port on the Dreamcast are very very very slim.

If the BBA is out of stock, most likely you will never see it back in stock there. Shortly after Sega released them, they stopped producing them, so there is a limited number of broadband adapters in the world. I would go ahead and buy one off of Ebay, because if you don't, you may never own one.

~The Masked M0M0~