Just bought a 1980 KZ750, good shape but is a project bike and need guidance.

It needs starter, and I am having problems finding one, Does anyone know of a compatible one or where a compatabily website/list is?

Howdy.  Is this a Twin or 750-4?  A 1980 model could be a 750G Twin or 750E/H 4-cylinder.
Partzilla has diagrams w a cross-reference. Find your model, then delve into the diagrams. click the part number for the x-ref. 

just in case. make sure the battery is good before assuming the starter is bad. charge it w a good motorcycle smart charger & do a load test. I use a Ctek US 0.8 & VC97 digital multimeter.

The starter motor itself does not often go bad. In most cases the problem is elsewhere. If you can provide a more detailed description of what is happening, folks here will be better able to offer useful advice.

If you open the menus for this website, click on Articles. Once that opens, you will see a choice for service manuals. There is a manual for the 750 E1 and H1, plus a manual for the 750 twins. These are the factory service manuals and will save you a great deal of grief and expense if you follow the instructions carefully. Be sure you get one that covers your exact year and model.

www.kzrider.com/service-manuals

I don't know of anyone who makes reproductions but I would try taking apart the starter motor. If you see a bunch of carbon / grease / general build up of crap in the brushes and commutators there is a very good chance you can fix it. I fixed multiple 'dead' kz440 starters by installing one of the starter rebuild kits to replace the brushes and by carefully scraping crud from out in-between the commutators with a razor blade. When putting it back together pay close attention to the gaskets and washers that connect the wire to the starter motor, if they aren't installed in the right order it is very easy to get an intermittent short.

I've heard it said that you shouldn't use something like carb cleaner because it can breakdown the epoxy that separates the winding coils and cause them to short out.

If you chose to go down the repair route (I did this for a living years ago at the start of my career as an auto electrician) before you fit the new brushs clean the commutator with emery tape and then, break an old hacksaw blade (tape up one end as a handle) then grind it to reduce the thickness. You then need to carefully run it between the copper segments of the commutator to "undercut" the insulator. These plastic insulators need to be lower than the copper or the brush's will not make full contact with the commutator as they will skip over the insulators. Given it a final clean with the emery tape and you will be good to go

Could be the starter clutch also so like said be sure of the battery and maybe describe how it acts after that.

I have seen this old article online, if you have the time feel free to read it: 

www.denniskirk.com/blog/2014/03/26/steps...torcycle-wont-start/