Sometimes I wonder about my bonsai brothers as to whether they have the resolve to do the things necessary to find good material or they are simply locked into a check book mentality. That's OK I don't have a problem with people who are willing to spend their resources for obtaining material for bonsai. Problem is; most sources for pre-bonsai do not carry Mugo Pines and Mugo Pines cannot be harvested from Yamadori sources in North America.
I have told people maybe a hundred times what they need to do to find good Mugo Pines in nurseries. I keep hearing the same things in return: "We don't have any Mugo Pines like the ones you find", refering to the trees I find. Most Mugos don't have single trunks, ---- the ones I find don't either, I employ a cut and grow technique to get single trunks on my trees.
The important thing is you have to be willing to get on your hands and knees and dig around in the pots under the branches to feel what the trunks are like. It is a messy proposition and does not always yield results. But good Mugos are out there, I located several within an hour at a nursery in Colorado this summer. I had to look they didn't just jump out at me but I found them.