This doesn't scan the USB printer themselves, but it lists the assets with USB printers attached. I don't believe LS has the capability to scan USB based printer directly.
Select Top 1000000 tsysOS.Image As Icon,
tblAssets.AssetID,
tblAssets.AssetName,
tblAssets.Domain,
tsysOS.OSname As OS,
tblAssets.SP,
tblAssets.IPAddress As IP,
tblPrinters.Caption As Printer,
tblPrinters.Portname As [Printer Port],
tblPrinters.Capabilitydescriptions As [Printer Capabilities],
tblPrinters.Lastchanged,
tblAssets.Username
From tblAssets
Inner Join tsysOS On tblAssets.OScode = tsysOS.OScode
Left Join tblPrinters On tblAssets.AssetID = tblPrinters.AssetID
Where (tblPrinters.Portname Like 'DOT4%' Or tblPrinters.Portname Like 'USB%')
And tblPrinters.Local = 1
Order By tblAssets.Domain,
tblAssets.AssetName,
Printer