<P>I was looking online on the different pumps (Bathmate, Penomet) and don't really feel like spending that kind of money just yet. Hence, I would like to try making my own pump. Can anyone give me any suggestions? </P>
This is one place where saving money is a "mixed bag" however there are ways to cut the bill down quite a bit. With regards to the pump itself go to either Harbor Freight or your local Auto Supply Store. There are very high quality vacuum pumps used in the automotive trades that are available for very low prices. This applies to both hand operated and electric.
The electric pumps are used for the evacuation before recharge of automobile air conditioning. If you watch the sales you can get a top grade electric for under $100 and if you want a brass trigger operated hand pump these are often found in areas where the parts for servicing brake systems are located. These can be used for bleeding brake systems.
While I agree that cutting costs on the pump is very important I would not agree on that approach with the cylinder. Cheap cylinders or poorly designed cylinders are an invitation to injury. If you look on the internet you can develop sources for the same thick wall lucite tubing that the vacuum pump manufacturers use in their cylinders. If you are good with tools and are a patient individual a clear lucite tube can easily be fashioned into a good cylinder with common things available at a hardware store. Remember however that the thickness of the wall of the tube is very important. The first reason is the danger of collapse and splintering under vacuum loads and the second is the ability to smooth and shape the contact edge that seals against your body. If you want a vacuum gauge again you can adapt from the automotive trades if your brake system pump does not have them by simply placing a T fitting in the suction line. There are vacuum lock clips and hobby plastic sources as well as your local hardware store that can supply about 95% of what you want easily.
Personally to get something that is not going to fracture or splinter easily under use you are in fact better of saving your money on the pump and spending it on the cylinder and the best out there are the thick wall cylinders from Vacu-Tech. This is very important and it is not worth taking a chance with the family jewels and sceptre. Good Luck