Then you probably want a Netopia PN660. v.35 serial port, NAT, RJ45 Ethernet, etc. They can't be upgraded with a Netopia OS later than 2 years ago due to flash and RAM limitations so they have limited VPN capability, but they work great for what they are. You can get them for < $25 on eBay.
This one is currently $9.99.
DO NOT buy a PN630/640 or any other model except the PN660 since that is the only one which will work for your specs. I would have given you one, but I threw them away a few months ago.
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