Raspberry Pi with USB Ethernet adapter

I'm trying to get a router & firewall going with a Pi 1B, the 256Mb RAM version. I have disabled dnsmasq as I have DNS & DHCP working well already. Most things are fine, but I want two Ethernet connections. I have a USB Ethernet adapter that works well with other Pis and uses the pegasus driver. I have found references to this driver here, but nothing telling me of a download site. Any advice would be appreciated.

kmod-usb-net kmod-usb-net-pegasus

being a pi... you'd probably have the other requisite kmod-usbX...

I see it now. I'd been looking for pegasus*. Now you've told me about the leading characters, I should be fine. Thank you.