Several people make them, D-Link, Linksys etc. you'll have to check compatibility with each of them but don't expect anything other than the printer to work. Most will not support the rest of the fuctionality of the MFC.
I am awaiting a new Brother MFC-420CN which has built in eithernet. It was $129 after rebate + a $30 store credit and should support full functionality accross the network. The print servers I looked at were all sort of around $80.
I'll have to report back after I get it set up.
Currently on a Pre-N Wireless Small Home-Office Network, running WindowsXP SP2, HP psc 2410c printer, Dell notebook