I own these, some are more than your budget:
TelecommunicationsAndNetworking.com (Long, but the classic phrase)
SunnyvaleComputer.com
Pair: NetworkOperation.com, WirelessNetworkOperation.com
NationalWirelessNetworks.com
Pair: NationalWimaxNetwork.com, NationalWimaxNetworks.com
Pair: P2pWirelessNetwork.com, P2pWirelessNetworks.com
ComputerDiagnosis.net
ComputerServers.org
Pair: OnDemandServers.com, OnDemandServer.com
LinuxComputers.net
Pair: EntryLevelComputer.com, EntryLevelComputers.com
Pair: MobileLinuxComputer.com, MobileLinuxComputers.com
Pair: GigaEthernet.com, TeraEthernet.com