My son built a SM version of his 08 model 300. He was lucky enough to find a set of GG wheels locally.
I have not heard of other wheels that fit right in without modifications, but (almost) anything can be made to fit if you have access to a lathe and a milling machine
In general the front wheel will be pretty easy to do, while the rear is more difficult as you have to search for a wheel with (almost) the same distance between sprocket and brake disk as the originals.
I have several wheel sets for my bikes so I can make any measurements you need. I can do it this week, but am quite busy so it may take a few days.
I have done wheel conversions on other bikes (fitted a set of PVM magnesium rims intended for a Ducati TT2 to my Bimota Supermono) so I know what it takes.
Depending on what you find on the secondhand market, I think you'll eventually find that the wheels from Motocrosscenter actually are quite affordable. Remember that the price includes disks and sprocket and even tires.
Regarding the front sprocket I don't really see the point in going bigger than 14, as there are plenty of smaller rear sprockets available.