That's a D1.1 modem also.
»www.newegg.com/Product/Product.a ··· 25122011
That should be within price ranges - i mean $50? Then again you can find those on eBay for like $15 or something too, just gotta be careful when buying them used as they might already be banned.
Try Amazon if that's better at $13.99
»www.amazon.com/Motorola-Surfboar ··· s=sb5100