Anyone who carries VDO gauges, also carries the senders. They even have them on Ebay.
The sender placement is kind of a "topic of discussion" on a lot of Air Cooled VW forums. You might want to check into ShopTalk Forums and run a search.
A lot of folks like to run the Gene Berg dip stick oil temp sensor, others use the VDO temp sender that threads into the drain plate in place of the drain plug.
Oil pressure is usually taken at the factory oil pressure sending switch hole in the block using a brass t-fitting and a standard VDO sender. The t-fitting will allow you to run a pressure sender to the gauge along with the stock warning light sender that goes to the light in the speedo.
I've also seen the pressure taken from the oil pump cover and the spacer that fits between the block and the factory oil cooler.
If you're planning on a remote oil cooler, you can pretty much put temp and pressure senders anywhere along the up-stream circuit. A second temp sender after the cooler is kind of cool as well, it'll let you know how well the cooler is functioning.
Luck,
TC
