You can build your own solar panel; the cost of this overall project will be around $100 or more, depending on how many watts you're hoping to get out of the panel. But for now let's look at a 60 watt package and the building of that. So read up and see how to build a solar panel yourself.
Purchasing solar cells will be your very first step. You can find these on eBay or many other places online. Check to see how they will be shipped, and if you are offered a guarantee in case they break during shipping. Many people will dip those cells into wax before shipping, which will help to protect them; however, it makes the cleaning up process a bit painful.
To build this 60 watt package you're going to need 36 solar cells. However, you may want to order more just in case some break. The box that will hold the finished solar cells shouldn't be very deep. In fact you should make it have sides of not more than three quarters of an inch. When you've made the box, ensure that your vent holes are large enough around half an inch should work best.
You will need to paint the box when it's completed. You won't need to use a certain color, white may seem to reflect the most, but it really won't matter the color you use. In order to get that wax off, if you have had the panels shipped in wax, you will need water with soap and water without soap. Get those two separate pots to almost boiling; you will place one cell in at a time. Using the plain hot water first, then moving it to the soapy water, do not pour that hot water down your drain; it will clog up your pipes.
Those solar cells will need to be soldered together, there are many different types of patterns that you can use to set this up look them up on the internet. It's best to only solder two solar cells at one time, and when you go to glue them down, place the silicone caulk in the center. Press down on the cells to get them onto the pegboard, and see if when it comes time to flip the board you can get another person to help.
You will need to interconnect those cells with each other. You can use either regular wire, or even copper braid, but make sure once you have six together that you test them. Place them into the box, and make sure that you screw them down on the board. Holding them into place is very important when you get them up on the roof.
You will need to connect the two half panels through a wire that will be placed into the vent holes. In order for the wire to be held into place, you should again use some silicone caulk. Don't forget your blocking diode, because you won't want your battery to discharge when it's cloudy out, or nighttime. Finally you can run your wires on the outside of the box, placing the Plexiglas over to protect the whole solar panel.
Your final step will be to add a plug so that you can turn the solar panel off and on as you wish. Oh and of course testing of the whole panel to make sure you have a working solar panel.