As I have 8 nintendo cabs, two of which have been converted to Single Monitor Playchoice 10s, I'll chime in a bit...
Finding single monitor PCBs and the carts to plug them in is fairly easy...ebay has them quite often. Finding a cage isn't hard either.
The wiring harness from a VS. is pretty close all in all to a PC10 single mon, however its missing some wires so you will have to be comfortable adding them yourself. Finding an actual Single mon PC10 harness intact is quite hard...in 2 years I've found one. The last one I saw go on ebay was in a NOS Single Mon kit that went for like $450 or so. If you would like the pin outs for a single mon PC, toss me a message and I'll send them to you. I've got them color coded to match the CPs
The hardest thing to find is an actual single monitor control panel. It took me close to a YEAR of hard searching to find my two, at a cost that I would rather not discuss (amazing how fast money goes when you are frustrated).
The solution I recommend would be to just keep it VS. Finding VS. boards and chips are rather easy, they all (for the most part) use the same control panel, and are fairly inexpensive. You can find things like Super Mario Bros, Tennis, Hogans Alley, Castlevania, RBI Baseball, Dr. Mario, Excitebike, Goonies, etc. PCB board with chips for about what just the PC10 carts cost. And they released for VS most of the games that came out for the PC10 (and some that didn't). The only difference is that you have to swap out the board each time you want to play a new game, rather than just hitting a button.
Either way, Nintendo cabs are a labor of love, they are alot of work but in the end are fantastic to have, play and love.
-Gumby
(edited to fix mispelling)