You can probably buy a rebuild kit for your clutch master cylinder here: http://www.siriusconinc.com
. Search by your model number like VF750 or V45 usually gets the best results.
Even if you get a used one the rubber has got to be so old that it may need to be rebuilt.
They might also have the screws at that site too.
If the heads are stripped it's probably because someone used a regular Phillips screwdriver on them. These screws are JIS (Japanese Industrial Standard). There's a thread on here about that too. Some of us has picked up a couple of nice JIS screwdrivers on Amazon.