I have a car with a PCV hose that is hard to find. Is there anyway I could reshape a similar diameter/length hose to make it fit? If I can't do it myself, could a mechanic do it?
Yes, it's possible to create your own custom hoses. PCV hoses can be anything from a short run of hose to a complex pipe with brackets depending on the car, so there's really no one general answer.
The biggest concerns are making sure that your custom hose doesn't kink or collapse, and that it stands up to the temperatures and chemicals it will be exposed to. Rubber hose tends to kink when making sharp turns, and many plastics are subject to deterioration from the oil and fumes, or to melting under heat.
Rubber hoses can be molded to shapes, but it's not easy to do at home.
If you're on a budget or just need a temporary solution, you can make do with a flexible length of durable hose that you route around as needed.
If your hose needs to make a sharp turn and that causes it to crimp, you can make a loop instead, as long as there's enough room for it. This is often the easiest and cheapest method, but it's not pretty.
If appearance is important, or you need to fit in a very cramped space, it's usually easier to bend copper or brass pipe to the desired shape (CPVC pipe may also be used if you're not too near exhaust.)
A common approach is to make a metal or PVC pipe shaped to fit in any confined spaces or tight bends, and put rubber hose sections at each end to make it easy to connect to your existing stems. Many OEM hoses are made this way. Here's an example.
You can also get sleeves and coils that can be used to help bend rubber hoses without kinking. Search for hose kink sleeves or hose benders. These are usually sleeves or springs that make it harder for the hose to flatten and prevent kinking. A spring style hose bender...
There are also many companies that specialize in making custom hoses and fittings if you're willing to spend more. Search for a custom hose fabricator in your area.