Several years ago I switch over to using a scalpel for all my precision cutting. My Xacto's still have a place in my work as ruff cutters and a #11blade held up side down to scribe a line for cutting, especially for wood as well as plastic. For that propose they are superb. For me I prefer a #3 and #5 Swann-Morton scalpel handles in metal with just three blade sizes for all my work A #10, #15, and #25a. With the #25a as the work horse of the lot. I still use an #1 Xacto handle for the scribe, mini saw blades, and custom made chisels from flat tip Xacto blades that I grind down on a grinder and sharpen with Japanese water stones. I cover the tips of the scalpel blades with a piece of bottle cork from wine bottles. I think a lot of what scalpel handle or any handle you use will be determined by the size of your hand more so then anything else. I have small hands so the #3 and #5 Swann-Morton's fit like a glove. Maybe a #6 or #7 Bard-Parker for larger hands. One thing to look for is that any handle scalpel or other wise feel like a natural extension of your arm and hand. You should not even notice that it is in your hand while working with one. Even as a medic back in 69-71 I never got cut while changing a scalpel blade. If you lift up on the back end of the blades tang and gently push forward the blades will usual disengage. For the rare troublesome ones I used the back of my Zippo lighter to push them out. Another trick is to wrap a piece of masking tape around the blade before you start to remove it. Wrap them in a piece of masking tape and dispose in the trash or place them in an old coffee can (plastic) and take them to the recycler when can is full. I keep mine stropped as I work on a Arkansa stone or a Japanese slurry stone. I prefer the water stones but the oil stones work just as well. It becomes a mater of which one you become comfortable with. It does not mater rather your working in boats, planes, or trains the mediums are very similar wood, plastic, and metal. The scalpel blades cut sharper and stay sharper longer, two the three times longer then the Xacto's. For me well worth the investment.
Now as to getting them. Become very good friends with your dentist and have him get them for you. If you go to a school check if they have a dental department. If you tell them what your up too they will more than likely gladly help you out and at a substantial discount. And last resort is the dential supply houses. Other responders on this list have clearly covered that. If I only had to have five tools the scalpel with blades would be one with a scale rule, a small square, Mimi Japanese pull saw, and Zess optics. Along with color correct lighting to clearly see what I am doing.