Hand saws types are generally defined by the size of the teeth and the angles they are sharpened at. I imagine it would be somewhat hard to find a new rip saw for sale these days, although it is quite easy to convert a crosscut saw to a rip saw simply by re-sharpening the teeth, keeping the file at 90 degrees to the saw blade during the proces and with no "down-angle" on the file handle (ie. horizontal). This is what distinguishes the "rip" from the "crosscut" - one cuts along the grain (rip) and one cuts across the grain. The panel saw is pretty much a cross cut saw with a smaller tooth size for more detailed work, although some (me) like to change the "rake" (forward angle) of the tooth a little.
Although the subtleties and difference in appearance is slight, the differing performance on each type of cut is dramatic. The rip saw cut tends to act like a series of little chisels cutting a square trench along the grain, while the crosscut acts like a series of left & right hand knife cuts neatly severing the fibres on each side of the cut. When the saw is properly sharpened you can quite clearly see this in action if you remove the saw from the timber and closely examine the kerf (saw cut). You would also generally prefer to have a tooth size of around 4-6 teeth per inch for a rip saw - quite large.
With the cost nowadays of a GMC power saw (not that I'd own one) at around $30-$40 the rip saw probably holds little appeal these days, and they can be hard work as well. If you wanted one I would look for a nice Disston handsaw (1950-1960 vintage) on eBay and send it off to the saw doctor for a clean-up and resharpening in the rip saw profile.
There's a lot to be said for the hardened point disposable saws which are every where these days. They last for ages under all sorts of use & abuse and you just chuck them when blunt and buy another for $20.00. However, I've still got my full set of hand saws in my saw bags and my sharpening clamp, even if I don't use them too often any more.
Don't Just Do it..... Do It HardenFast!