> I'm wondering if the scanner lamp needs replacing?
Most likely yes.
> and where would I aquire such a lamp these days?
Consult with the Google for part numbers and resellers
> I've tried the hp printing supplies store, but there the printer isn't listed.
You wont find the parts there. Its going to have to come from a 3rd party parts reseller. WHat is going to be key in your search is finding the actual part number. Once you have that in your hands finding matches will be much easier.
LaserJets have the advantage of Service Manuals where inkjet products do not. I would start by looking up a Service Manual for your pritner and then dig through it for the part number that you need. Chances are good that you wont find a bulb by itself and would likely need to purchase an entire Scanner Assembly. Those are simple to swap out, usually only connected with a few screws and a cable or ribbon of some kind.